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Title: Height-dependent Velocity Structure of Photospheric Convection in Granules and Intergranular Lanes with Hinode /SOT

Abstract

The solar photosphere is the visible surface of the Sun, where many bright granules, surrounded by narrow dark intergranular lanes, are observed everywhere. The granular pattern is a manifestation of convective motion at the photospheric level, but its velocity structure in the height direction is poorly understood observationally. Applying bisector analysis to a photospheric spectral line recorded by the Hinode Solar Optical Telescope, we derived the velocity structure of the convective motion in granular regions and intergranular lanes separately. The amplitude of motion of the convective material decreases from 0.65 to 0.40 km s{sup −1} as the material rises in granules, whereas the amplitude of motion increases from 0.30 to 0.50 km s{sup −1} as it descends in intergranular lanes. These values are significantly larger than those obtained in previous studies using bisector analysis. The acceleration of descending materials with depth is not predicted from the convectively stable condition in a stratified atmosphere. Such convective instability can be developed more efficiently by radiative cooling and/or a gas pressure gradient, which can control the dynamical behavior of convective material in intergranular lanes. Our analysis demonstrated that bisector analysis is a useful method for investigating the long-term dynamic behavior of convective materialmore » when a large number of pixels is available. In addition, one example is the temporal evolution of granular fragmentation, in which downflowing material develops gradually from a higher layer downward.« less

Authors:
 [1];  [2];  [3]
  1. Department of Space and Astronautical Science/SOKENDAI (The Graduate University for Advanced Studies), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)
  2. Department of Science and Technology/Kwansei Gakuin University, Gakuen 2-1, Sanda, Hyogo 669-1337 (Japan)
  3. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)
Publication Date:
OSTI Identifier:
22663872
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 836; 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; ACCELERATION; AMPLITUDES; CONVECTION; CONVECTIVE INSTABILITIES; EVOLUTION; FRAGMENTATION; GRANULATION; LAYERS; PHOTOSPHERE; PRESSURE GRADIENTS; RADIATIVE COOLING; SUN; SURFACES; TELESCOPES

Citation Formats

Oba, T., Iida, Y., and Shimizu, T., E-mail: oba.takayoshi@ac.jaxa.jp. Height-dependent Velocity Structure of Photospheric Convection in Granules and Intergranular Lanes with Hinode /SOT. United States: N. p., 2017. Web. doi:10.3847/1538-4357/836/1/40.
Oba, T., Iida, Y., & Shimizu, T., E-mail: oba.takayoshi@ac.jaxa.jp. Height-dependent Velocity Structure of Photospheric Convection in Granules and Intergranular Lanes with Hinode /SOT. United States. doi:10.3847/1538-4357/836/1/40.
Oba, T., Iida, Y., and Shimizu, T., E-mail: oba.takayoshi@ac.jaxa.jp. Fri . "Height-dependent Velocity Structure of Photospheric Convection in Granules and Intergranular Lanes with Hinode /SOT". United States. doi:10.3847/1538-4357/836/1/40.
@article{osti_22663872,
title = {Height-dependent Velocity Structure of Photospheric Convection in Granules and Intergranular Lanes with Hinode /SOT},
author = {Oba, T. and Iida, Y. and Shimizu, T., E-mail: oba.takayoshi@ac.jaxa.jp},
abstractNote = {The solar photosphere is the visible surface of the Sun, where many bright granules, surrounded by narrow dark intergranular lanes, are observed everywhere. The granular pattern is a manifestation of convective motion at the photospheric level, but its velocity structure in the height direction is poorly understood observationally. Applying bisector analysis to a photospheric spectral line recorded by the Hinode Solar Optical Telescope, we derived the velocity structure of the convective motion in granular regions and intergranular lanes separately. The amplitude of motion of the convective material decreases from 0.65 to 0.40 km s{sup −1} as the material rises in granules, whereas the amplitude of motion increases from 0.30 to 0.50 km s{sup −1} as it descends in intergranular lanes. These values are significantly larger than those obtained in previous studies using bisector analysis. The acceleration of descending materials with depth is not predicted from the convectively stable condition in a stratified atmosphere. Such convective instability can be developed more efficiently by radiative cooling and/or a gas pressure gradient, which can control the dynamical behavior of convective material in intergranular lanes. Our analysis demonstrated that bisector analysis is a useful method for investigating the long-term dynamic behavior of convective material when a large number of pixels is available. In addition, one example is the temporal evolution of granular fragmentation, in which downflowing material develops gradually from a higher layer downward.},
doi = {10.3847/1538-4357/836/1/40},
journal = {Astrophysical Journal},
number = 1,
volume = 836,
place = {United States},
year = {Fri Feb 10 00:00:00 EST 2017},
month = {Fri Feb 10 00:00:00 EST 2017}
}
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