A mighty burst of electrically charged particles blasting from the sun’s surface during an April storm squashed the 8-million mile plasma tail of Encke’s comet, which caused the comet’s own magnetic field lines to touch. The tail was severed in the rebound.

Off With Its Head

"It was pretty amazing," Angelos Vourlidas, a solar physicist with the Naval Research Laboratory in Washington D.C., told Discovery News.

"We were basically following the comet because we know it was going to come in our images, so we were looking at our movies every day. Suddenly we saw (the storm) coming from the right-hand side of the sun and we thought ‘Well this is just a random occurrence. It will just pass over the comet.’

"But once (the storm) reached the comet, it cut the tail," Vourlidas said. "We could see the tail moving in the solar wind like a flag in the wind, making waves and flapping all around."
The comet was left a bare rock, with its severed tail wrapped around the front of the solar storm, known as a coronal mass ejection.

Within five hours, the comet formed a new and even longer tail. The old tail dissipated as it was blasted through space.

Scientists had known comet tails were vulnerable even before the spacecraft called STEREO caught the mutilation in the act. They didn’t realize, however, how quickly the tail could go, nor the mechanism for its detachment.

The comet tail, which is made of electrified gas, was squeezed by the storm’s magnetic field, which spirals out like a Slinky.

Eventually, the magnetic field around the comet tail was so squashed that its two sides, which are oppositely orientated, touched, triggering a burst of energy that chopped off the tail. The whole process took less than two hours.

"That’s pretty fast on a cosmic scale," Vourlidas said. "We didn’t expect that."

The discovery raises questions for solar physicists as well.

"We study CMEs (coronal mass ejections) all day. We thought we knew everything about them but seeing them interacting with a comet gives you a bird’s eye view of what happens when the CME comes to Earth because it probably does something very similar with Earth’s magnetic tail," Vourlidas said.

The finding also confirms that the solar storms, which can hobble satellites, radio communications and power grids on Earth, are magnetic, Vourlidas said.

Researchers will be reporting their discovery in next week’s Astrophysical Journal Letters

Via: Discovery