Ca II 854.2 nm BISECTORS AND CIRCUMFACULAR REGIONS

Pietarila, A.; Harvey, J. W.

doi:10.1088/0004-637X/764/2/153

Title: Ca II 854.2 nm BISECTORS AND CIRCUMFACULAR REGIONS

Full Record
Other Related Research

Abstract

Active regions appear bright in Ca II 854.2 nm line core intensity while the surrounding areas, referred to as circumfacular regions, are darker than the active region or the quiet Sun. We use Synoptic Optical Long-term Investigations of the Sun Vector Spectromagnetograph Ca II 854.2 nm data (photospheric and chromospheric full disk magnetograms as well as high spectral resolution Stokes I and V profiles) to study the connection between magnetic canopies, circumfacular regions, and Ca II 854.2 nm bisector amplitudes (spans). The line bisector amplitude is reduced in circumfacular regions, where the 3 minute period power in chromospheric H{alpha} intensity oscillations is also reduced relative to the surrounding quiet Sun. The latter is consistent with magnetic canopies in circumfacular regions suppressing upward propagating steepening acoustic waves. Our results provide further strong evidence for shock waves as the cause of the inverse C-shaped bisector and explain the observed solar cycle variation of the shape and amplitude of Sun-as-a-star Ca II 854.2 nm bisectors.

Authors:

Pietarila, A.; Harvey, J. W. ^[1]

National Solar Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States)

Publication Date:: Wed Feb 20 00:00:00 EST 2013

OSTI Identifier:: 22167733

Resource Type:: Journal Article

Journal Name:: Astrophysical Journal

Additional Journal Information:: Journal Volume: 764; 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; AMPLITUDES; ASTRONOMY; ASTROPHYSICS; CALCIUM IONS; CHROMOSPHERE; EMISSION SPECTRA; LINE WIDTHS; OSCILLATIONS; PHOTOSPHERE; RESOLUTION; SHOCK WAVES; SOLAR CYCLE; SOUND WAVES; SUN; WAVE PROPAGATION

Citation Formats


                    Pietarila, A., and Harvey, J. W. Ca II 854.2 nm BISECTORS AND CIRCUMFACULAR REGIONS.  United States: N. p., 2013. 
        Web.  doi:10.1088/0004-637X/764/2/153.

Copy to clipboard


                    Pietarila, A., & Harvey, J. W. Ca II 854.2 nm BISECTORS AND CIRCUMFACULAR REGIONS.  United States.  https://doi.org/10.1088/0004-637X/764/2/153

Copy to clipboard


                    Pietarila, A., and Harvey, J. W. 2013.  
        "Ca II 854.2 nm BISECTORS AND CIRCUMFACULAR REGIONS".  United States.  https://doi.org/10.1088/0004-637X/764/2/153.

Copy to clipboard


                    
@article{osti_22167733,

  title        = {Ca II 854.2 nm BISECTORS AND CIRCUMFACULAR REGIONS},

  author       = {Pietarila, A. and Harvey, J. W.},

  abstractNote = {Active regions appear bright in Ca II 854.2 nm line core intensity while the surrounding areas, referred to as circumfacular regions, are darker than the active region or the quiet Sun. We use Synoptic Optical Long-term Investigations of the Sun Vector Spectromagnetograph Ca II 854.2 nm data (photospheric and chromospheric full disk magnetograms as well as high spectral resolution Stokes I and V profiles) to study the connection between magnetic canopies, circumfacular regions, and Ca II 854.2 nm bisector amplitudes (spans). The line bisector amplitude is reduced in circumfacular regions, where the 3 minute period power in chromospheric H{alpha} intensity oscillations is also reduced relative to the surrounding quiet Sun. The latter is consistent with magnetic canopies in circumfacular regions suppressing upward propagating steepening acoustic waves. Our results provide further strong evidence for shock waves as the cause of the inverse C-shaped bisector and explain the observed solar cycle variation of the shape and amplitude of Sun-as-a-star Ca II 854.2 nm bisectors.},

  doi          = {10.1088/0004-637X/764/2/153},

  url          = {https://www.osti.gov/biblio/22167733},
  journal      = {Astrophysical Journal},

  issn         = {0004-637X},

  number       = 2,

  volume       = 764,

  place        = {United States},

  year         = {Wed Feb 20 00:00:00 EST 2013},

  month        = {Wed Feb 20 00:00:00 EST 2013}

}

Copy to clipboard

Journal Article:

https://doi.org/10.1088/0004-637X/764/2/153

Other availability

Find in Google Scholar

Search WorldCat to find libraries that may hold this journal

Save / Share:

Export Metadata

Save to My Library

Similar records in OSTI.GOV collections:

SOLAR CYCLE VARIATION IN SUN-AS-A-STAR Ca II 854.2 nm BISECTORS

Journal Article Pietarila, A; Livingston, W - Astrophysical Journal

The bisector of the strong chromospheric Ca II 854.2 nm line has an inverse-C shape, the cause of which is not yet fully understood. We show that the amplitude of the bisector in Sun-as-a-star observations exhibits a solar cycle variation with smaller amplitudes during highest activity. The line core intensity is lower during solar minima while the part of the bisector most sensitive to the line core shows no systematic change with activity. Our results support the use of Ca II 854.2 nm bisectors in studying the relationship between convection and magnetic fields, not only in the Sun but inmore » other stars as well.« less
https://doi.org/10.1088/0004-637X/736/2/114
THE EFFECT OF ISOTOPIC SPLITTING ON THE BISECTOR AND INVERSIONS OF THE SOLAR Ca II 854.2 nm LINE

Journal Article Leenaarts, Jorrit; Carlsson, Mats; Kochukhov, Oleg - Astrophysical Journal Letters

The Ca II 854.2 nm spectral line is a common diagnostic of the solar chromosphere. The average line profile shows an asymmetric core, and its bisector shows a characteristic inverse-C shape. The line actually consists of six components with slightly different wavelengths depending on the isotope of calcium. This isotopic splitting of the line has been taken into account in studies of non-solar stars, but never for the Sun. We performed non-LTE radiative transfer computations from three models of the solar atmosphere and show that the line-core asymmetry and inverse C-shape of the bisector of the 854.2 nm line can be explainedmore »« less
https://doi.org/10.1088/2041-8205/784/1/L17
SYNOPTIC MAPPING OF CHROMOSPHERIC MAGNETIC FLUX

Journal Article Jin, C.; Harvey, J. - Astrophysical Journal

We used daily full-disk Ca II 854.2 nm magnetograms from the Synoptic Optical Long Term Investigations of the Sun (SOLIS) facility to study the chromospheric magnetic field from 2006 April through 2009 November. We determined and corrected previously unidentified zero offsets in the SOLIS magnetograms. By tracking the disk passages of stable unipolar regions, the measured net flux densities were found to systematically decrease from the disk center to the limb by a factor of about two. This decrease was modeled using a thin flux tube model with a difference in signal formation height between the center and limb sides.more »« less
https://doi.org/10.1088/0004-637X/765/2/79
THE EVOLUTION OF DARK CANOPIES AROUND ACTIVE REGIONS

Journal Article Wang, Y; Robbrecht, E; Muglach, K - Astrophysical Journal

As observed in spectral lines originating from the chromosphere, transition region, and low corona, active regions are surrounded by an extensive 'circumfacular' area which is darker than the quiet Sun. We examine the properties of these dark moat- or canopy-like areas using Fe IX 17.1 nm images and line-of-sight magnetograms from the Solar Dynamics Observatory. The 17.1 nm canopies consist of fibrils (horizontal fields containing extreme-ultraviolet-absorbing chromospheric material) clumped into featherlike structures. The dark fibrils initially form a quasiradial or vortical pattern as the low-lying field lines fanning out from the emerging active region connect to surrounding network and intranetworkmore »« less
https://doi.org/10.1088/0004-637X/733/1/20
EVIDENCE FOR TWO SEPARATE BUT INTERLACED COMPONENTS OF THE CHROMOSPHERIC MAGNETIC FIELD

Journal Article Reardon, K; Wang, Y; Warren, H; ... - Astrophysical Journal

Chromospheric fibrils are generally thought to trace out low-lying, mainly horizontal magnetic fields that fan out from flux concentrations in the photosphere. A high-resolution ({approx}0.''1 pixel{sup -1}) image, taken in the core of the Ca II 854.2 nm line and covering an unusually large area, shows the dark fibrils within an active region remnant as fine, looplike features that are aligned parallel to each other and have lengths comparable to a supergranular diameter. Comparison with simultaneous line-of-sight magnetograms confirms that the fibrils are centered above intranetwork areas (supergranular cell interiors), with one end rooted just inside the neighboring plage ormore »« less
https://doi.org/10.1088/0004-637X/742/2/119

Similar Records