Pulsars flicker because of electric funnels in their magnetic field ✦
Diocotron instability is like a ‘vortex’ in the plasma around a pulsar, growing and creating a rotating asymmetry. It can mix charges and alter the radiation, explaining oddities in pulsar flickering. Imagine an elusive dance of charges making a stellar lighthouse fade and flash.
A pulsar is a super-dense neutron star left over after a supernova explosion. It spins rapidly, holding a cloud of plasma with its magnetic field. The plasma rotates unevenly: faster near the axis than at the edges. This difference spawns electric funnels—like a whirlpool. They grow in just a few rotations of the star (which for an Earth observer stretch out due to the immense gravity). The funnels stir up charges and fling them toward the light cylinder—the outer boundary of the magnetosphere. There, particles disrupt the radio signal, causing the pulsar to flicker or fall silent altogether.
Astronomers detect these changes using spectroscopy: they break radio waves into frequencies, tracking how the funnels distort the emission. Now the variability of pulsars has a clear cause.
🎯 The strength of the electric funnel is just a couple percent of the pulsar's total charge, but that's enough to make this cosmic lighthouse flicker.
🎬 In Carl Sagan's 'Contact,' aliens turned a pulsar into a beacon; nature does just fine without them: electric funnels turn the star into a twinkling transmitter all on their own.