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Title: Spectroscopic study of a dark lane and a cool loop in a solar limb active region by Hinode/EIS

We investigated a cool loop and a dark lane over a limb active region on 2007 March 14 using the Hinode/EUV Imaging Spectrometer. The cool loop is clearly seen in the spectral lines formed at the transition region temperature. The dark lane is characterized by an elongated faint structure in the coronal spectral lines and is rooted on a bright point. We examined their electron densities, Doppler velocities, and nonthermal velocities as a function of distance from the limb. We derived electron densities using the density sensitive line pairs of Mg VII, Si X, Fe XII, Fe XIII, and Fe XIV spectra. We also compared the observed density scale heights with the calculated scale heights from each peak formation temperatures of the spectral lines under the hydrostatic equilibrium. We noted that the observed density scale heights of the cool loop are consistent with the calculated heights, with the exception of one observed cooler temperature; we also found that the observed scale heights of the dark lane are much lower than their calculated scale heights. The nonthermal velocity in the cool loop slightly decreases along the loop, while nonthermal velocity in the dark lane sharply falls off with height. Such amore » decrease in the nonthermal velocity may be explained by wave damping near the solar surface or by turbulence due to magnetic reconnection near the bright point.« less
Authors:
 [1] ;  [2] ; ;  [3]
  1. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara-shi, Kanagawa 252-5210 (Japan)
  2. Solar-Terretrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan)
  3. Department of Astronomy and Space Science, Kyung Hee University, Yongin 446-701 (Korea, Republic of)
Publication Date:
OSTI Identifier:
22348207
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 780; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CHROMOSPHERE; COMPARATIVE EVALUATIONS; DENSITY; DOPPLER EFFECT; ELECTRON DENSITY; ELEMENT ABUNDANCE; EQUILIBRIUM; EXCEPTIONS; HEAT EXCHANGERS; LIMBS; MAGNETIC RECONNECTION; SCALE HEIGHT; SPECTRA; SPECTROMETERS; SUN; SURFACES; TURBULENCE; ULTRAVIOLET RADIATION; VELOCITY