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Title: Asymmetries in coronal spectral lines and emission measure distribution

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. Here we address 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 also 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.
Authors:
 [1] ;  [2]
  1. Inter-University Centre for Astronomy and Astrophysics, Post Bag-4, Ganeshkhind, Pune 411007 (India)
  2. NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
Publication Date:
OSTI Identifier:
22348568
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 779; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALTITUDE; ASYMMETRY; DISTRIBUTION; EMISSION; EVAPORATION; HEAT; HEAT EXCHANGERS; MASS; PLASMA; SOLAR CORONA; SOLAR PROMINENCES; SUN; ULTRAVIOLET RADIATION