Physicists caught protons ‘surfing’ on shock waves

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Protons can surf some truly gnarly waves.

A new experiment suggests that the subatomic particles can be accelerated by a process akin to surfers catching waves. The protons get a speed boost not from ocean swells, but from shock waves within plasma, a mixture of electrically charged particles. Such shock waves are sonic boom–like disturbances marked by an abrupt increase in density, temperature and pressure.

The research could help scientists better understand some of the high-energy particles that zip through the cosmos. Shock waves in space are thought to propel charged particles, but it’s still not fully understood how particles get their pep (SN: 11/12/20).

In the experiment, which mimicked certain types of cosmic shock waves, protons reached energies up to 80,000 electron volts, physicists report August 19 in Nature Physics. In space, similar shock waves occur where the outflow of charged particles from the sun meets the Earth’s magnetic field, for example, and also where those particles slow down dramatically as they approach the edge of the solar system, at what’s called the termination shock (SN: 10/4/13).

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