On the Parallel and Perpendicular Propagating Motions Visible in Polar Plumes: An Incubator For (Fast) Solar Wind Acceleration?

TL;DR

This study combines observations from CoMP and AIA to analyze Alfvenic motions and intensity disturbances in polar plumes, revealing their potential role in solar wind acceleration through MHD turbulence.

Contribution

It provides new observational evidence of parallel and perpendicular propagating motions in polar plumes and discusses their implications for solar wind acceleration.

Findings

Alfvenic wave motions have a phase speed of 830 km/s and a period of 5 minutes.

Intensity perturbations have an apparent speed of 120 km/s and a 15-minute period.

The observed motions may contribute to the turbulence needed for fast solar wind acceleration.

Abstract

We combine observations of the Coronal Multi-channel Polarimeter (CoMP) and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) to study the characteristic properties of (propagating) Alfvenic motions and quasi-periodic intensity disturbances in polar plumes. This unique combination of instruments highlights the physical richness of the processes taking place at the base of the (fast) solar wind. The (parallel) intensity perturbations with intensity enhancements around 1% have an apparent speed of 120 km/s (in both the 171A and 193A passbands) and a periodicity of 15 minutes, while the (perpendicular) Alfvenic wave motions have a velocity amplitude of 0.5 km/s, a phase speed of 830 km/s, and a shorter period of 5 minutes on the same structures. These observations illustrate a scenario where the excited Alfvenic motions are propagating along an inhomogeneously loaded magnetic field structure such that the combination could be a potential progenitor of the magnetohydrodynamic turbulence required to accelerate the fast solar wind.