Asymmetries in Coronal Spectral lines and Emission Measure Distribution

Abstract

It has previously been argued that 1. spicules do not provide enough pre-heated plasma to fill the corona, and 2. even if they did, additional heating would be required to keep the plasma hot as it expands upward. We here address the question of whether spicules play an important role by injecting plasma at cooler temperatures ($<2$ MK), which then gets heated to coronal values at higher altitudes. We measure red-blue asymmetries in line profiles formed over a wide range of temperatures in the bright moss areas of two active regions. We derive emission measure distributions from the excess wing emission. We find that the asymmetries and emission measures are small and conclude that spicules do not inject an important (dominant) mass flux into the cores of active regions at temperatures $>0.6$ MK ($\log T>5.8$). These conclusions apply not only to spicules, but to any process that suddenly heats and accelerates chromospheric plasma (e.g., a chromospheric nanoflare). The traditional picture of coronal heating and chromospheric evaporation appears to remain the most likely explanation of the active region corona.

18 pages, 7 figures, Accepted for publication in ApJ

References in corpus (4)

• Observing the Roots of Solar Coronal Heating - in the Chromosphere
• Two components of the coronal emission revealed by EUV spectroscopic observations
• The Role of Type II Spicules in the Upper Solar Atmosphere
• Density structure of an active region and associated moss using Hinode/EIS

Cited by in corpus (21)

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• Solar UV and X-Ray Spectral Diagnostics
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• Observations and numerical models of solar coronal heating associated with spicules
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• The solar chromosphere observed at 1 Hz and 0."2 resolution
• Spectroscopic Observations of a Coronal Loop: Basic Physical Plasma Parameters Along the Full Loop Length
• Chromospheric Nanoflares as a Source of Coronal Plasma: II. Repeating Nanoflares
• X-ray Spectral Components in the Afterglow of GRB 130925A
• Core and Wing Densities of Asymmetric Coronal Spectral Profiles: Implications for the Mass Supply of the Solar Corona
• An Observational Study of a "Rosetta-Stone" Solar Eruption
• ALMA and IRIS Observations of the Solar Chromosphere I: an On-Disk Type II Spicule
• High--cadence observations of spicular-type events on the Sun
• Heating and cooling of coronal loops observed by SDO
• MHD modeling of coronal loops: injection of high-speed chromospheric flows
• A survey of eight hot Jupiters in secondary eclipse using WIRCam at CFHT
• Contribution of spicules to solar coronal emission
• Plasma injection into a solar coronal loop
• Propagating Disturbances along fan-like coronal loops in an active region
• Line Profile Studies of Coronal Active Regions in Fe XII λ195.12 Using Hinode/EIS
• Active region upflows in various coronal structures and their coupling to the lower atmosphere