Turbulence

Turbulence in the solar wind is a key driver of plasma dynamics, transferring energy from large-scale structures to smaller scales where it can heat particles and accelerate them. This process is not uniform; it depends on factors like wind speed, magnetic field alignment, and distance from the Sun. By studying wave-particle interactions and the intermittent nature of turbulent fluctuations, we can better understand how the solar wind evolves as it travels through the heliosphere and what that means for predicting its impact on planetary environments.

Figure showing the distribution of near-Earth solar wind speeds during solar minima with key speeds highlighted. — The solar wind is filled with fluctuations. The most common are associated with Alfvén waves, the simplest type of wave in a magnetized plasma. The solar wind can't achieve the fastest, non-transient speeds observed near Earth ( $v_{fast}$ ) without continued acceleration once it leaves the Sun. This acceleration is likely driven by Alfvén waves as they dissipate during the solar wind's transit through interplantery space. The intermediate range of speeds ( $v_{IP}$ ) likely corresponds to solar wind from solar sources like coronal holes for which the energy in the Alfvénic fluctuations is too low to accelerate it to the fastest, non-transient speeds observed near Earth. From Alterman (2025), The Astrophysical Journal Letters.