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Title: PERSISTENT DOPPLER SHIFT OSCILLATIONS OBSERVED WITH HINODE/EIS IN THE SOLAR CORONA: SPECTROSCOPIC SIGNATURES OF ALFVENIC WAVES AND RECURRING UPFLOWS

Abstract

Using data obtained by the EUV Imaging Spectrometer on board Hinode, we have performed a survey of obvious and persistent (without significant damping) Doppler shift oscillations in the corona. We have found mainly two types of oscillations from February to April in 2007. One type is found at loop footpoint regions, with a dominant period around 10 minutes. They are characterized by coherent behavior of all line parameters (line intensity, Doppler shift, line width, and profile asymmetry), and apparent blueshift and blueward asymmetry throughout almost the entire duration. Such oscillations are likely to be signatures of quasi-periodic upflows (small-scale jets, or coronal counterpart of type-II spicules), which may play an important role in the supply of mass and energy to the hot corona. The other type of oscillation is usually associated with the upper part of loops. They are most clearly seen in the Doppler shift of coronal lines with formation temperatures between one and two million degrees. The global wavelets of these oscillations usually peak sharply around a period in the range of three to six minutes. No obvious profile asymmetry is found and the variation of the line width is typically very small. The intensity variation is oftenmore » less than 2%. These oscillations are more likely to be signatures of kink/Alfven waves rather than flows. In a few cases, there seems to be a {pi}/2 phase shift between the intensity and Doppler shift oscillations, which may suggest the presence of slow-mode standing waves according to wave theories. However, we demonstrate that such a phase shift could also be produced by loops moving into and out of a spatial pixel as a result of Alfvenic oscillations. In this scenario, the intensity oscillations associated with Alfvenic waves are caused by loop displacement rather than density change. These coronal waves may be used to investigate properties of the coronal plasma and magnetic field.« less

Authors:
;  [1]; ;  [2];  [3]; ;  [4]
  1. High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States)
  2. Department of Physics, Catholic University of America, Washington, DC 20064 (United States)
  3. Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover St., Org. ADBS, Bldg. 252, Palo Alto, CA 94304 (United States)
  4. Max Planck Institute for Solar System Research, 37191 Katlenburg-Lindau (Germany)
Publication Date:
OSTI Identifier:
22086378
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 759; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALFVEN WAVES; ASTRONOMY; ASTROPHYSICS; ASYMMETRY; DAMPING; DENSITY; DOPPLER EFFECT; EXTREME ULTRAVIOLET SPECTRA; LINE WIDTHS; MAGNETIC FIELDS; OSCILLATIONS; PERIODICITY; PHASE SHIFT; PLASMA; SOLAR CORONA; SOLAR PROMINENCES; SOLAR WIND; STANDING WAVES; SUN

Citation Formats

Tian Hui, McIntosh, Scott W., Wang, Tongjiang, Ofman, Leon, De Pontieu, Bart, Innes, Davina E., and Peter, Hardi, E-mail: htian@ucar.edu. PERSISTENT DOPPLER SHIFT OSCILLATIONS OBSERVED WITH HINODE/EIS IN THE SOLAR CORONA: SPECTROSCOPIC SIGNATURES OF ALFVENIC WAVES AND RECURRING UPFLOWS. United States: N. p., 2012. Web. doi:10.1088/0004-637X/759/2/144.
Tian Hui, McIntosh, Scott W., Wang, Tongjiang, Ofman, Leon, De Pontieu, Bart, Innes, Davina E., & Peter, Hardi, E-mail: htian@ucar.edu. PERSISTENT DOPPLER SHIFT OSCILLATIONS OBSERVED WITH HINODE/EIS IN THE SOLAR CORONA: SPECTROSCOPIC SIGNATURES OF ALFVENIC WAVES AND RECURRING UPFLOWS. United States. doi:10.1088/0004-637X/759/2/144.
Tian Hui, McIntosh, Scott W., Wang, Tongjiang, Ofman, Leon, De Pontieu, Bart, Innes, Davina E., and Peter, Hardi, E-mail: htian@ucar.edu. Sat . "PERSISTENT DOPPLER SHIFT OSCILLATIONS OBSERVED WITH HINODE/EIS IN THE SOLAR CORONA: SPECTROSCOPIC SIGNATURES OF ALFVENIC WAVES AND RECURRING UPFLOWS". United States. doi:10.1088/0004-637X/759/2/144.
@article{osti_22086378,
title = {PERSISTENT DOPPLER SHIFT OSCILLATIONS OBSERVED WITH HINODE/EIS IN THE SOLAR CORONA: SPECTROSCOPIC SIGNATURES OF ALFVENIC WAVES AND RECURRING UPFLOWS},
author = {Tian Hui and McIntosh, Scott W. and Wang, Tongjiang and Ofman, Leon and De Pontieu, Bart and Innes, Davina E. and Peter, Hardi, E-mail: htian@ucar.edu},
abstractNote = {Using data obtained by the EUV Imaging Spectrometer on board Hinode, we have performed a survey of obvious and persistent (without significant damping) Doppler shift oscillations in the corona. We have found mainly two types of oscillations from February to April in 2007. One type is found at loop footpoint regions, with a dominant period around 10 minutes. They are characterized by coherent behavior of all line parameters (line intensity, Doppler shift, line width, and profile asymmetry), and apparent blueshift and blueward asymmetry throughout almost the entire duration. Such oscillations are likely to be signatures of quasi-periodic upflows (small-scale jets, or coronal counterpart of type-II spicules), which may play an important role in the supply of mass and energy to the hot corona. The other type of oscillation is usually associated with the upper part of loops. They are most clearly seen in the Doppler shift of coronal lines with formation temperatures between one and two million degrees. The global wavelets of these oscillations usually peak sharply around a period in the range of three to six minutes. No obvious profile asymmetry is found and the variation of the line width is typically very small. The intensity variation is often less than 2%. These oscillations are more likely to be signatures of kink/Alfven waves rather than flows. In a few cases, there seems to be a {pi}/2 phase shift between the intensity and Doppler shift oscillations, which may suggest the presence of slow-mode standing waves according to wave theories. However, we demonstrate that such a phase shift could also be produced by loops moving into and out of a spatial pixel as a result of Alfvenic oscillations. In this scenario, the intensity oscillations associated with Alfvenic waves are caused by loop displacement rather than density change. These coronal waves may be used to investigate properties of the coronal plasma and magnetic field.},
doi = {10.1088/0004-637X/759/2/144},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 759,
place = {United States},
year = {2012},
month = {11}
}