Distant Black Hole Wave Twists like Giant Whip

Fast-moving magnetic waves emanating from a distant supermassive black hole undulate like a whip whose handle is being shaken by a giant hand, according to a new study using National Radio Astronomy Observatory’s Very Long Baseline Array. Scientists used this instrument to explore the galaxy/black hole system known as BL Lacertae (BL Lac) in high resolution.
The findings help researchers understand how black holes produce jets.

“The waves are excited by a shaking motion of the jet at its base,” said David Meier. It’s the 1st time Alfven waves have been identified in a black hole system. They are generated when magnetic field lines, such as those from the sun or a disk around a black hole, interact with ions, and become twisted or coiled into a helical shape. In the case of BL Lac, the ions are in the form of particle jets that are flung from opposite sides of the black hole at near light speed.
The Alfven waves are analogous to the propagating sideways motions of a slinky, and as the waves propagate along the magnetic field lines, they can cause the field lines—and the particle jets encompassed by the field lines—to move as well.
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