On the Nature of Propagating Intensity Disturbances in Polar Plumes during the 2017 Total Solar Eclipse

TL;DR

This study analyzes propagating intensity disturbances in polar coronal plumes during the 2017 solar eclipse, revealing they are likely a mix of slow magnetoacoustic waves and plasma outflows, with speeds varying by temperature and activity level.

Contribution

It provides the first detailed analysis of PIDs in polar plumes during a solar eclipse, distinguishing between wave and flow components based on multi-wavelength observations.

Findings

PIDs in higher temperature channels are faster than in cooler channels.

Speed ratio (~1.3) matches the theoretical value for slow magnetoacoustic waves.

Active plumes show more significant speed differences than quiet plumes.

Abstract

The propagating intensity disturbances (PIDs) in plumes are still poorly understood and their identity (magnetoacoustic waves or flows) remains an open question. We investigate PIDs in five plumes located in the northern polar coronal hole observed during the 2017 total solar eclipse. Three plumes are associated with coronal bright points, jets and macrospicules at their base (active plumes) and the other two plumes are not (quiet plumes). The electron temperature at the base of the plumes is obtained from the filter ratio of images taken with the X-ray Telescope on board Hinode and the passband ratio around 400 nm from an eclipse instrument, the Diagnostic Coronagraph Experiment (DICE). The phase speed (v_r), frequency (omega), and wavenumber (k) of the PIDs in the plumes are obtained by applying a Fourier transformation to the space-time (r-t plane) plots in images taken with the Atmospheric Imaging Assembly (AIA) in three different wavelength channels (171 A, 193 A, and 211 A). We found that the PIDs in the higher temperature AIA channels, 193 and 211 A, are faster than that of the cooler AIA 171 A channel. This tendency is more significant for the active plumes than the quiet ones. The observed speed ratio (~1.3) between the AIA 171 and 193 A channels is similar to the theoretical value (1.25) of a slow magnetoacoustic wave. Our results support the idea that PIDs in plumes represent a superposition of slow magnetoacoustic waves and plasma outflows that consist of dense cool flows and hot coronal jets.