A chromospheric resonance cavity in a sunspot mapped with seismology

David Jess, Ben Snow, Scott Houston, Gert Botha, Bernhard Fleck, S. Krishna Prasad, Andres Asensio Ramos, Richard Morton, Peter Keys, Shahin Jafarzadeh, Marco Stangalini, Samuel Grant, Damian Christian

Research output: Contribution to journalLetter

Abstract

Sunspots are intense collections of magnetic fields that pierce through the Sun’s photosphere, with their signatures extending upwards into the outermost extremities of the solar corona. Cutting-edge observations and simulations are providing insights into the underlying wave generation, configuration and damping mechanisms found in sunspot atmospheres. However, the in situ amplification of magnetohydrodynamic waves, rising from a few hundreds of metres per second in the photosphere to several kilometres per second in the chromosphere, has, until now, proved difficult to explain. Theory predicts that the enhanced umbral wave power found at chromospheric heights may come from the existence of an acoustic resonator, which is created due to the substantial temperature gradients experienced at photospheric and transition region heights. Here, we provide strong observational evidence of a resonance cavity existing above a highly magnetic sunspot. Through a combination of spectropolarimetric inversions and comparisons with high-resolution numerical simulations, we provide a new seismological approach to mapping the geometry of the inherent temperature stratifications across the diameter of the underlying sunspot, with the upper boundaries of the chromosphere ranging between 1,300 ± 200 km and 2,300 ± 250 km. Our findings will allow the three-dimensional structure of solar active regions to be conclusively determined from relatively commonplace two-dimensional Fourier power spectra. The techniques presented are also readily suitable for investigating temperature-dependent resonance effects in other areas of astrophysics, including the examination of Earth–ionosphere wave cavities.
Original languageEnglish
Number of pages16
JournalNature Astronomy
Early online date02 Dec 2019
DOIs
Publication statusEarly online date - 02 Dec 2019

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seismology
sunspots
cavities
chromosphere
photosphere
wave generation
solar corona
magnetohydrodynamic waves
stratification
power spectra
temperature gradients
astrophysics
simulation
examination
damping
resonators
signatures
inversions
atmospheres
temperature

Cite this

Jess, David ; Snow, Ben ; Houston, Scott ; Botha, Gert ; Fleck, Bernhard ; Krishna Prasad, S. ; Asensio Ramos, Andres ; Morton, Richard ; Keys, Peter ; Jafarzadeh, Shahin ; Stangalini, Marco ; Grant, Samuel ; Christian, Damian. / A chromospheric resonance cavity in a sunspot mapped with seismology. In: Nature Astronomy. 2019.
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abstract = "Sunspots are intense collections of magnetic fields that pierce through the Sun’s photosphere, with their signatures extending upwards into the outermost extremities of the solar corona. Cutting-edge observations and simulations are providing insights into the underlying wave generation, configuration and damping mechanisms found in sunspot atmospheres. However, the in situ amplification of magnetohydrodynamic waves, rising from a few hundreds of metres per second in the photosphere to several kilometres per second in the chromosphere, has, until now, proved difficult to explain. Theory predicts that the enhanced umbral wave power found at chromospheric heights may come from the existence of an acoustic resonator, which is created due to the substantial temperature gradients experienced at photospheric and transition region heights. Here, we provide strong observational evidence of a resonance cavity existing above a highly magnetic sunspot. Through a combination of spectropolarimetric inversions and comparisons with high-resolution numerical simulations, we provide a new seismological approach to mapping the geometry of the inherent temperature stratifications across the diameter of the underlying sunspot, with the upper boundaries of the chromosphere ranging between 1,300 ± 200 km and 2,300 ± 250 km. Our findings will allow the three-dimensional structure of solar active regions to be conclusively determined from relatively commonplace two-dimensional Fourier power spectra. The techniques presented are also readily suitable for investigating temperature-dependent resonance effects in other areas of astrophysics, including the examination of Earth–ionosphere wave cavities.",
author = "David Jess and Ben Snow and Scott Houston and Gert Botha and Bernhard Fleck and {Krishna Prasad}, S. and {Asensio Ramos}, Andres and Richard Morton and Peter Keys and Shahin Jafarzadeh and Marco Stangalini and Samuel Grant and Damian Christian",
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Jess, D, Snow, B, Houston, S, Botha, G, Fleck, B, Krishna Prasad, S, Asensio Ramos, A, Morton, R, Keys, P, Jafarzadeh, S, Stangalini, M, Grant, S & Christian, D 2019, 'A chromospheric resonance cavity in a sunspot mapped with seismology', Nature Astronomy. https://doi.org/10.1038/s41550-019-0945-2

A chromospheric resonance cavity in a sunspot mapped with seismology. / Jess, David; Snow, Ben; Houston, Scott; Botha, Gert; Fleck, Bernhard; Krishna Prasad, S.; Asensio Ramos, Andres; Morton, Richard; Keys, Peter; Jafarzadeh, Shahin; Stangalini, Marco; Grant, Samuel; Christian, Damian.

In: Nature Astronomy, 02.12.2019.

Research output: Contribution to journalLetter

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AU - Jess, David

AU - Snow, Ben

AU - Houston, Scott

AU - Botha, Gert

AU - Fleck, Bernhard

AU - Krishna Prasad, S.

AU - Asensio Ramos, Andres

AU - Morton, Richard

AU - Keys, Peter

AU - Jafarzadeh, Shahin

AU - Stangalini, Marco

AU - Grant, Samuel

AU - Christian, Damian

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N2 - Sunspots are intense collections of magnetic fields that pierce through the Sun’s photosphere, with their signatures extending upwards into the outermost extremities of the solar corona. Cutting-edge observations and simulations are providing insights into the underlying wave generation, configuration and damping mechanisms found in sunspot atmospheres. However, the in situ amplification of magnetohydrodynamic waves, rising from a few hundreds of metres per second in the photosphere to several kilometres per second in the chromosphere, has, until now, proved difficult to explain. Theory predicts that the enhanced umbral wave power found at chromospheric heights may come from the existence of an acoustic resonator, which is created due to the substantial temperature gradients experienced at photospheric and transition region heights. Here, we provide strong observational evidence of a resonance cavity existing above a highly magnetic sunspot. Through a combination of spectropolarimetric inversions and comparisons with high-resolution numerical simulations, we provide a new seismological approach to mapping the geometry of the inherent temperature stratifications across the diameter of the underlying sunspot, with the upper boundaries of the chromosphere ranging between 1,300 ± 200 km and 2,300 ± 250 km. Our findings will allow the three-dimensional structure of solar active regions to be conclusively determined from relatively commonplace two-dimensional Fourier power spectra. The techniques presented are also readily suitable for investigating temperature-dependent resonance effects in other areas of astrophysics, including the examination of Earth–ionosphere wave cavities.

AB - Sunspots are intense collections of magnetic fields that pierce through the Sun’s photosphere, with their signatures extending upwards into the outermost extremities of the solar corona. Cutting-edge observations and simulations are providing insights into the underlying wave generation, configuration and damping mechanisms found in sunspot atmospheres. However, the in situ amplification of magnetohydrodynamic waves, rising from a few hundreds of metres per second in the photosphere to several kilometres per second in the chromosphere, has, until now, proved difficult to explain. Theory predicts that the enhanced umbral wave power found at chromospheric heights may come from the existence of an acoustic resonator, which is created due to the substantial temperature gradients experienced at photospheric and transition region heights. Here, we provide strong observational evidence of a resonance cavity existing above a highly magnetic sunspot. Through a combination of spectropolarimetric inversions and comparisons with high-resolution numerical simulations, we provide a new seismological approach to mapping the geometry of the inherent temperature stratifications across the diameter of the underlying sunspot, with the upper boundaries of the chromosphere ranging between 1,300 ± 200 km and 2,300 ± 250 km. Our findings will allow the three-dimensional structure of solar active regions to be conclusively determined from relatively commonplace two-dimensional Fourier power spectra. The techniques presented are also readily suitable for investigating temperature-dependent resonance effects in other areas of astrophysics, including the examination of Earth–ionosphere wave cavities.

U2 - 10.1038/s41550-019-0945-2

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M3 - Letter

JO - Nature Astronomy

JF - Nature Astronomy

SN - 2397-3366

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