A turbulent journey toward understanding space plasma dynamics

Charged particles from the sun arrive at Earth too fast to dodge it. As a result, they collide with the planet’s magnetosphere, triggering a shock wave called the bow shock and sending ripples through the plasma to the magnetic and electric fields that permeate space. This disruption could help explain how turbulence works in space.

Turbulence is the primary method by which energy transfers from larger scales to smaller ones. Often, energy transfer can be explained through particle collisions, but these are rare in the vacuum of space. The physics of plasma could lend needed insight.

Plank and Gingell investigated how the bow shock disrupts turbulence in plasma. They used in-situ measurements of the magnetic spectrum, intermittency of ripples in the magnetic field, and the size of large structures from NASA’s Magnetospheric Multiscale mission to form a picture of turbulence.

“There are measurable differences in turbulence when looking at areas of space before the bow shock and after, indicating that a shock discontinuity can affect the turbulence,” said author James Plank.

The turbulence rebound time is on the order of seconds to minutes, depending on the size of the discontinuity and the angle at which the magnetic field intersects with the shock.

“Our results show that turbulence appears to be very difficult to get rid of in space plasmas,” said Plank. “Collisions with planetary bow shocks are one of the most dramatic things that can happen to a plasma in space, so to find that fully developed turbulence recovers so rapidly indicates that it is not a fragile state that occurs only in precisely balanced situations, but rather a mostly fundamental part of space plasma behavior.”

Source: “Intermittency at Earth’s bow shock: Measures of turbulence in quasi-parallel and quasi-perpendicular shocks,” by J. Plank and I. L. Gingell, Physics of Plasmas (2023). The article can be accessed at https://doi.org/10.1063/5.0160439 .