Measurements of Outflow Velocities in On-Disk Plumes from EIS Hinode Observations

Abstract

The contribution of plumes to the solar wind has been subject to hot debate in the past decades. The EUV Imaging Spectrometer (EIS) on board Hinode provides a unique means to deduce outflow velocities at coronal heights via direct Doppler shift measurements of coronal emission lines. Such direct Doppler shift measurements were not possible with previous spectrometers. We measure the outflow velocity at coronal heights in several on-disk long-duration plumes, which are located in coronal holes and show significant blue shifts throughout the entire observational period. In one case, a plume is measured 4 hours apart. The deduced outflow velocities are consistent, suggesting that the flows are quasi-steady. Furthermore, we provide an outflow velocity profile along the plumes, finding that the velocity corrected for the line-of-sight effect can reach 10 km s${}^{-1}$ at 1.02 $R_{\odot }$, 15 km s${}^{-1}$ at 1.03 $R_{\odot }$, and 25 km s${}^{-1}$ at 1.05 $R_{\odot }$. This clear signature of steady acceleration, combined with the fact that there is no significant blue shift at the base of plumes, provides an important constraint on plume models. At the height of 1.03 $R_{\odot }$, EIS also deduced a density of 1.3$\times 10^8$ cm${}^{-3}$, resulting in a proton flux of about 4.2$\times 10^9$ cm${}^{-2}$s${}^{-1}$ scaled to 1AU, which is an order of magnitude higher than the proton input to a typical solar wind if a radial expansion is assumed. This suggests that, coronal hole plumes may be an important source of the solar wind.

arXiv commentaccepted for publication in ApJ, 13 pages, 9 figures

References in corpus (15)

• EUV emission lines and diagnostics observed with Hinode/EIS
• High precision density measurements in the solar corona: I. Analysis methods and results for Fe XII and Fe XIII
• Signatures of Alfven waves in the polar coronal holes as seen by EIS/Hinode
• Observation of High-speed Outflow on Plume-like Structures of the Quiet Sun and Coronal Holes with SDO/AIA
• Coronal hole boundaries evolution at small scales: II. XRT view Can small-scale outflows at CHBs be a source of the slow solar wind?
• Morphology, dynamics and plasma parameters of plumes and inter-plume regions in solar coronal holes
• Identification of the Coronal Sources of the Fast Solar Wind
• Evidence for polar jets as precursors of polar plume formation
• STEREO Observations of Quasi-Periodically Driven High Velocity Outflows in Polar Plumes
• Velocity Structure of Jets in Coronal Hole
• Fake star formation bursts: blue horizontal branch stars masquerade as young stars in optical integrated light spectroscopy
• The nascent fast solar wind observed by EIS onboard Hinode
• Coronal hole boundaries at small scales: III. EIS and SUMER views
• The quiet Sun average Doppler shift of coronal lines up to 2 MK
• Stereoscopic Polar Plume Reconstructions from Stereo/Secchi Images

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• On the relation between transition region network jets and coronal plumes
• Two-stage energy release process of a confined flare with double HXR peaks
• Critical magnetic field strengths for solar coronal plumes in quiet regions and coronal holes?
• Scattered light in the Hinode/EIS and SDO/AIA instruments measured from the 2012 Venus transit
• Prospective Implications of EUV Coronal Plumes for Magnetic-network Genesis of Coronal Heating, Coronal-hole Solar Wind, and Solar-wind Magnetic-field Switchbacks
• Statistical properties of Hα jets in the polar coronal hole and their implications in coronal activities
• Contribution of polar plumes to fast solar wind
• Population of Bright Plume Threads in Solar Polar Coronal Holes
• High-resolution observations of small-scale activity in coronal hole plumes