STEREO Observations of Quasi-Periodically Driven High Velocity Outflows in Polar Plumes

Abstract

Plumes are one of the most ubiquitous features seen at the limb in polar coronal holes and are considered to be a source of high density plasma streams to the fast solar wind. We analyze STEREO observations of plumes and aim to reinterpret and place observations with previous generations of EUV imagers within a new context that was recently developed from Hinode observations. We exploit the higher signal-to-noise, spatial and temporal resolution of the EUVI telescopes over that of SOHO/EIT to study the temporal variation of polar plumes in high detail. We employ recently developed insight from imaging (and spectral) diagnostics of active region, plage, and quiet Sun plasmas to identify the presence of apparent motions as high-speed upflows in magnetic regions as opposed to previous interpretations of propagating waves. In almost all polar plumes observed at the limb in these STEREO sequences, in all coronal passbands, we observe high speed jets of plasma traveling along the structures with a mean velocity of 135km/s at a range of temperatures from 0.5-1.5MK. The jets have an apparent brightness enhancement of ~5% above that of the plumes they travel on and repeat quasi-periodically, with repeat-times ranging from five to twenty-five minutes. We also notice a very weak, fine scale, rapidly evolving, but ubiquitous companion of the plumes that covers the entire coronal hole limb. The observed jets are remarkably similar in intensity enhancement, periodicity and velocity to those observed in other magnetic regions of the solar atmosphere. They are multi-thermal in nature. We infer that the jets observed on the plumes are a source of heated mass to the fast solar wind. Further, based on the previous results that motivated this study, we suggest that these jets originated in the upper chromosphere.

4 pages, 4 figures. Accepted to appear in A&A Letters. Movies supporting the Letter can be found in http://download.hao.ucar.edu/pub/mscott/papers/Plumes/

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Cited by in corpus (14)

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• The Spectroscopic Signature of Quasi-periodic Upflows in Active Region Timeseries
• Observation of High-speed Outflow on Plume-like Structures of the Quiet Sun and Coronal Holes with SDO/AIA
• Generation of quasi-periodic waves and flows in the solar atmosphere by oscillatory reconnection
• Rotating Solar Jets in Simulations of Flux Emergence with Thermal Conduction
• Propagating intensity disturbances in polar corona as seen from AIA/SDO
• Accelerating waves in polar coronal holes as seen by EIS and SUMER
• Spectroscopic Observations of Propagating Disturbances in a Polar Coronal Hole: Evidence of Slow Magneto-acoustic Waves
• Two-fluid numerical simulations of solar spicules
• Measurements of Outflow Velocities in On-Disk Plumes from EIS Hinode Observations
• On the Parallel and Perpendicular Propagating Motions Visible in Polar Plumes: An Incubator For (Fast) Solar Wind Acceleration?
• Accelerating and Supersonic Density Fluctuations in Coronal Hole Plumes: Signature of Nascent Solar Winds