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Fleck B, Carlsson M, Khomenko E, Rempel M, Steiner O, Vigeesh G. Acoustic-gravity wave propagation characteristics in three-dimensional radiation hydrodynamic simulations of the solar atmosphere. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2021; 379:20200170. [PMID: 33342376 DOI: 10.1098/rsta.2020.0170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 07/09/2020] [Indexed: 06/12/2023]
Abstract
There has been tremendous progress in the degree of realism of three-dimensional radiation magneto-hydrodynamic simulations of the solar atmosphere in the past decades. Four of the most frequently used numerical codes are Bifrost, CO5BOLD, MANCHA3D and MURaM. Here we test and compare the wave propagation characteristics in model runs from these four codes by measuring the dispersion relation of acoustic-gravity waves at various heights. We find considerable differences between the various models. The height dependence of wave power, in particular of high-frequency waves, varies by up to two orders of magnitude between the models, and the phase difference spectra of several models show unexpected features, including ±180° phase jumps. This article is part of the Theo Murphy meeting issue 'High-resolution wave dynamics in the lower solar atmosphere'.
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Affiliation(s)
- B Fleck
- ESA Science and Operations Department, c/o NASA/GSFC Code 671, Greenbelt, MD 20771, USA
| | - M Carlsson
- Rosseland Centre for Solar Physics, University of Oslo, Postboks 1029 Blindern, 0315 Oslo, Norway
- Institute of Theoretical Astrophysics, University of Oslo, Postboks 1029 Blindern, 0315 Oslo, Norway
| | - E Khomenko
- Instituto de Astrofísica de Canarias, La Laguna, 38205 Tenerife, Spain
- Departamento de Astrofísica, Universidad de La Laguna, La Laguna, 38205 Tenerife, Spain
| | - M Rempel
- High Altitude Observatory, NCAR, PO Box 3000, Boulder, CO 80307, USA
| | - O Steiner
- Leibniz-Institut für Sonnenphysik (KIS), Schöneckstrasse 6, 79104 Freiburg, Germany
- Istituto Ricerche Solari Locarno (IRSOL), Via Patocchi 57, 6605 Locarno-Monti, Switzerland
| | - G Vigeesh
- Leibniz-Institut für Sonnenphysik (KIS), Schöneckstrasse 6, 79104 Freiburg, Germany
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Hanasoge SM, Hotta H, Sreenivasan KR. Turbulence in the Sun is suppressed on large scales and confined to equatorial regions. SCIENCE ADVANCES 2020; 6:eaba9639. [PMID: 32923604 PMCID: PMC7450475 DOI: 10.1126/sciadv.aba9639] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/19/2020] [Accepted: 06/05/2020] [Indexed: 06/11/2023]
Abstract
Convection in the Sun's outer envelope generates turbulence and drives differential rotation, meridional circulation, and the global magnetic cycle. We develop a greater understanding of these processes by contrasting observations with simulations of global convection. These comparisons also enhance our comprehension of the physics of distant Sun-like stars. Here, we infer toroidal flow power as a function of wave number, frequency, and depth in the solar interior through helioseismic analyses of space-based observations. The inferred flows grow with spatial wave number and temporal frequency and are confined to low latitudes, supporting the argument that rotation induces systematic differences between the poles and equator. In contrast, the simulations used here show the opposite trends-power diminishing with increasing wave number and frequency while flow amplitudes become weakest at low latitudes. These differences highlight gaps in our understanding of solar convection and point to challenges ahead.
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Affiliation(s)
- Shravan M. Hanasoge
- Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Mumbai, India
- Center for Space Science, New York University, Abu Dhabi, UAE
| | | | - Katepalli R. Sreenivasan
- Center for Space Science, New York University, Abu Dhabi, UAE
- New York University, New York, NY, USA
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Peter H, Tian H, Curdt W, Schmit D, Innes D, De Pontieu B, Lemen J, Title A, Boerner P, Hurlburt N, Tarbell TD, Wuelser JP, Martínez-Sykora J, Kleint L, Golub L, McKillop S, Reeves KK, Saar S, Testa P, Kankelborg C, Jaeggli S, Carlsson M, Hansteen V. Hot explosions in the cool atmosphere of the Sun. Science 2014; 346:1255726. [PMID: 25324397 DOI: 10.1126/science.1255726] [Citation(s) in RCA: 203] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The solar atmosphere was traditionally represented with a simple one-dimensional model. Over the past few decades, this paradigm shifted for the chromosphere and corona that constitute the outer atmosphere, which is now considered a dynamic structured envelope. Recent observations by the Interface Region Imaging Spectrograph (IRIS) reveal that it is difficult to determine what is up and down, even in the cool 6000-kelvin photosphere just above the solar surface: This region hosts pockets of hot plasma transiently heated to almost 100,000 kelvin. The energy to heat and accelerate the plasma requires a considerable fraction of the energy from flares, the largest solar disruptions. These IRIS observations not only confirm that the photosphere is more complex than conventionally thought, but also provide insight into the energy conversion in the process of magnetic reconnection.
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Affiliation(s)
- H Peter
- Max Planck Institute for Solar System Research, 37077 Göttingen, Germany.
| | - H Tian
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
| | - W Curdt
- Max Planck Institute for Solar System Research, 37077 Göttingen, Germany
| | - D Schmit
- Max Planck Institute for Solar System Research, 37077 Göttingen, Germany
| | - D Innes
- Max Planck Institute for Solar System Research, 37077 Göttingen, Germany
| | - B De Pontieu
- Lockheed Martin Solar and Astrophysics Laboratory (LMSAL), 3251 Hanover Street, Building 252, Palo Alto, CA 94304, USA. Institute of Theoretical Astrophysics, University of Oslo, Post Office Box 1029, Blindern, NO-0315 Oslo, Norway
| | - J Lemen
- Lockheed Martin Solar and Astrophysics Laboratory (LMSAL), 3251 Hanover Street, Building 252, Palo Alto, CA 94304, USA
| | - A Title
- Lockheed Martin Solar and Astrophysics Laboratory (LMSAL), 3251 Hanover Street, Building 252, Palo Alto, CA 94304, USA
| | - P Boerner
- Lockheed Martin Solar and Astrophysics Laboratory (LMSAL), 3251 Hanover Street, Building 252, Palo Alto, CA 94304, USA
| | - N Hurlburt
- Lockheed Martin Solar and Astrophysics Laboratory (LMSAL), 3251 Hanover Street, Building 252, Palo Alto, CA 94304, USA
| | - T D Tarbell
- Lockheed Martin Solar and Astrophysics Laboratory (LMSAL), 3251 Hanover Street, Building 252, Palo Alto, CA 94304, USA
| | - J P Wuelser
- Lockheed Martin Solar and Astrophysics Laboratory (LMSAL), 3251 Hanover Street, Building 252, Palo Alto, CA 94304, USA
| | - Juan Martínez-Sykora
- Lockheed Martin Solar and Astrophysics Laboratory (LMSAL), 3251 Hanover Street, Building 252, Palo Alto, CA 94304, USA. Bay Area Environmental Research Institute, 596 1st Street West, Sonoma, CA 95476, USA
| | - L Kleint
- Lockheed Martin Solar and Astrophysics Laboratory (LMSAL), 3251 Hanover Street, Building 252, Palo Alto, CA 94304, USA. Bay Area Environmental Research Institute, 596 1st Street West, Sonoma, CA 95476, USA. NASA Ames Research Center, Moffett Field, CA 94305, USA
| | - L Golub
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
| | - S McKillop
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
| | - K K Reeves
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
| | - S Saar
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
| | - P Testa
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
| | - C Kankelborg
- Department of Physics, Montana State University, Bozeman, Post Office Box 173840, Bozeman, MT 59717, USA
| | - S Jaeggli
- Department of Physics, Montana State University, Bozeman, Post Office Box 173840, Bozeman, MT 59717, USA
| | - M Carlsson
- Institute of Theoretical Astrophysics, University of Oslo, Post Office Box 1029, Blindern, NO-0315 Oslo, Norway
| | - V Hansteen
- Institute of Theoretical Astrophysics, University of Oslo, Post Office Box 1029, Blindern, NO-0315 Oslo, Norway
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Felipe T, Crouch AD, Birch AC. EVALUATION OF THE CAPABILITY OF LOCAL HELIOSEISMOLOGY TO DISCERN BETWEEN MONOLITHIC AND SPAGHETTI SUNSPOT MODELS. THE ASTROPHYSICAL JOURNAL 2014; 788:136. [PMID: 29670299 PMCID: PMC5901914 DOI: 10.1088/0004-637x/788/2/136] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The helioseismic properties of the wave scattering generated by monolithic and spaghetti sunspots are analyzed by means of numerical simulations. In these computations, an incident f- or p1-mode travels through the sunspot model, which produces absorption and phase shift of the waves. The scattering is studied by inspecting the wavefield, computing travel-time shifts, and performing Fourier-Hankel analysis. The comparison between the results obtained for both sunspot models reveals that the differences in the absorption coefficient can be detected above noise level. The spaghetti model produces a steep increase of the phase shift with the degree of the mode at short wavelengths, while mode mixing is more efficient for the monolithic model. These results provide a clue for what to look for in solar observations to discern the constitution of sunspots between the proposed monolithic and spaghetti models.
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Affiliation(s)
- T Felipe
- NorthWest Research Associates, Colorado Research Associates, Boulder, CO 80301, USA
| | - A D Crouch
- NorthWest Research Associates, Colorado Research Associates, Boulder, CO 80301, USA
| | - A C Birch
- Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen, Germany
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Rempel M. Numerical models of sunspot formation and fine structure. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2012; 370:3114-3128. [PMID: 22665895 DOI: 10.1098/rsta.2011.0556] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Sunspots are central to our understanding of solar (and stellar) magnetism in many respects. On the large scale, they link the magnetic field observable in the photosphere to the dynamo processes operating in the solar interior. Properly interpreting the constraints that sunspots impose on the dynamo process requires a detailed understanding of the processes involved in their formation, dynamical evolution and decay. On the small scale, they give an insight into how convective energy transport interacts with the magnetic field over a wide range of field strengths and inclination angles, leading to sunspot fine structure observed in the form of umbral dots and penumbral filaments. Over the past decade, substantial progress has been made on both observational and theoretical sides. Advanced ground- and space-based observations have resolved, for the first time, the details of umbral dots and penumbral filaments and discovered similarities in their substructures. Numerical models have advanced to the degree that simulations of entire sunspots with sufficient resolution to resolve sunspot fine structure are feasible. A combination of improved helioseismic inversion techniques with seismic forward modelling provides new views on the subsurface structure of sunspots. In this review, we summarize recent progress, with particular focus on numerical modelling.
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Affiliation(s)
- Matthias Rempel
- High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO 80307, USA.
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Borrero JM, Ichimoto K. Magnetic Structure of Sunspots. LIVING REVIEWS IN SOLAR PHYSICS 2011; 8:4. [PMID: 27194965 PMCID: PMC4841203 DOI: 10.12942/lrsp-2011-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
UNLABELLED In this review we give an overview about the current state-of-knowledge of the magnetic field in sunspots from an observational point of view. We start by offering a brief description of tools that are most commonly employed to infer the magnetic field in the solar atmosphere with emphasis in the photosphere of sunspots. We then address separately the global and local magnetic structure of sunspots, focusing on the implications of the current observations for the different sunspots models, energy transport mechanisms, extrapolations of the magnetic field towards the corona, and other issues. ELECTRONIC SUPPLEMENTARY MATERIAL Supplementary material is available for this article at 10.12942/lrsp-2011-4.
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Affiliation(s)
- Juan M. Borrero
- />Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, Freiburg, D-79104 Germany
| | - Kiyoshi Ichimoto
- />Kwasan and Hida Observatories, Kyoto University, Yamashina, Kyoto, 607-8471 Japan
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Scharmer GB, Henriques VMJ, Kiselman D, de la Cruz Rodríguez J. Detection of convective downflows in a sunspot penumbra. Science 2011; 333:316-9. [PMID: 21636742 DOI: 10.1126/science.1206429] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The fine structure and dynamics of sunspots and the strong outflow in their outer filamentary part--the penumbra--have puzzled astronomers for more than a century. Recent theoretical models and three-dimensional numerical simulations explain the penumbral filaments and their radiative energy output as the result of overturning convection. Here, we describe the detection of ubiquitous, relatively dark downward flows of up to 1 kilometer per second (km/s) in the interior penumbra, using imaging spectropolarimetric data from the Swedish 1-meter Solar Telescope. The dark downflows are omnipresent in the interior penumbra, distinguishing them from flows in arched flux tubes, and are associated with strong (3 to 3.5 km/s) radial outflows. They are thus part of a penumbral convective flow pattern, with the Evershed flow representing the horizontal component of that convection.
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Affiliation(s)
- G B Scharmer
- Institute for Solar Physics of the Royal Swedish Academy of Sciences, and Department of Astronomy at Stockholm University, AlbaNova University Center, SE-10691 Stockholm, Sweden.
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