The Coronal Power Spectrum from MHD Mode Conversion above Sunspots
Sunspots are intense regions of magnetic flux that are rooted deep below the photosphere. It is well established that sunspots host magnetohydrodynamic waves, with numerous observations showing a connection to the internal acoustic (or p- )modes of the Sun. The p- modes are fast waves below the equi...
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2025-01-01
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| author | Hemanthi Miriyala Richard J. Morton Elena Khomenko Patrick Antolin Gert J.J. Botha |
| author_facet | Hemanthi Miriyala Richard J. Morton Elena Khomenko Patrick Antolin Gert J.J. Botha |
| author_sort | Hemanthi Miriyala |
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| description | Sunspots are intense regions of magnetic flux that are rooted deep below the photosphere. It is well established that sunspots host magnetohydrodynamic waves, with numerous observations showing a connection to the internal acoustic (or p- )modes of the Sun. The p- modes are fast waves below the equipartition layer and are thought to undergo a double mode conversion as they propagate upward into the atmosphere of sunspots, which can generate Alfvénic modes in the upper atmosphere. We employ 2.5D magnetohydrodynamic numerical simulations to investigate the adiabatic wave propagation and examine the resulting power spectra of coronal Alfvénic waves. A broadband wave source is used, which has a 1D power spectrum mimicking aspects of the observed p- mode power spectrum. We examine magnetoacoustic wave propagation and mode conversion from the photosphere to the corona. Frequency filtering of the upwardly propagating acoustic waves is a natural consequence of a gravitationally stratified atmosphere and plays a key role in shaping the power spectra of mode-converted waves. We demonstrate that the slow and fast magnetoacoustic waves and Alfvén waves above the equipartition layer have similarly shaped power spectra, which are modified versions of the driver spectrum. Notably, the results reveal that the coronal wave power spectra have a peak at a higher frequency than that of the underlying p -mode driver. This matches observations of coronal Alfvénic waves and further supports the role of the mode conversion process as a mechanism for Alfvénic wave generation in the Sun's atmosphere. |
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| institution | Kabale University |
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| language | English |
| publishDate | 2025-01-01 |
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| spelling | doaj-art-3443afb3391e4889ba629a3ccf5207772025-01-29T06:26:01ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01979223610.3847/1538-4357/ada26fThe Coronal Power Spectrum from MHD Mode Conversion above SunspotsHemanthi Miriyala0https://orcid.org/0000-0002-2235-3216Richard J. Morton1https://orcid.org/0000-0001-5678-9002Elena Khomenko2https://orcid.org/0000-0003-3812-620XPatrick Antolin3https://orcid.org/0000-0003-1529-4681Gert J.J. Botha4https://orcid.org/0000-0002-5915-697XDepartment of Mathematics, Physics and Electrical Engineering, Northumbria University , Newcastle upon Tyne, NE1 8ST, UK ; hemanthi.miriyala@northumbria.ac.ukDepartment of Mathematics, Physics and Electrical Engineering, Northumbria University , Newcastle upon Tyne, NE1 8ST, UK ; hemanthi.miriyala@northumbria.ac.ukInstituto de Astrofísica de Canarias , 38205, La Laguna, Tenerife, Spain; Departamento de Astrofísica, Universidad de La Laguna , 38205, La Laguna, Tenerife, SpainDepartment of Mathematics, Physics and Electrical Engineering, Northumbria University , Newcastle upon Tyne, NE1 8ST, UK ; hemanthi.miriyala@northumbria.ac.ukDepartment of Mathematics, Physics and Electrical Engineering, Northumbria University , Newcastle upon Tyne, NE1 8ST, UK ; hemanthi.miriyala@northumbria.ac.ukSunspots are intense regions of magnetic flux that are rooted deep below the photosphere. It is well established that sunspots host magnetohydrodynamic waves, with numerous observations showing a connection to the internal acoustic (or p- )modes of the Sun. The p- modes are fast waves below the equipartition layer and are thought to undergo a double mode conversion as they propagate upward into the atmosphere of sunspots, which can generate Alfvénic modes in the upper atmosphere. We employ 2.5D magnetohydrodynamic numerical simulations to investigate the adiabatic wave propagation and examine the resulting power spectra of coronal Alfvénic waves. A broadband wave source is used, which has a 1D power spectrum mimicking aspects of the observed p- mode power spectrum. We examine magnetoacoustic wave propagation and mode conversion from the photosphere to the corona. Frequency filtering of the upwardly propagating acoustic waves is a natural consequence of a gravitationally stratified atmosphere and plays a key role in shaping the power spectra of mode-converted waves. We demonstrate that the slow and fast magnetoacoustic waves and Alfvén waves above the equipartition layer have similarly shaped power spectra, which are modified versions of the driver spectrum. Notably, the results reveal that the coronal wave power spectra have a peak at a higher frequency than that of the underlying p -mode driver. This matches observations of coronal Alfvénic waves and further supports the role of the mode conversion process as a mechanism for Alfvénic wave generation in the Sun's atmosphere.https://doi.org/10.3847/1538-4357/ada26fMagnetohydrodynamical simulationsSolar coronal wavesAlfvén wavesSunspots |
| spellingShingle | Hemanthi Miriyala Richard J. Morton Elena Khomenko Patrick Antolin Gert J.J. Botha The Coronal Power Spectrum from MHD Mode Conversion above Sunspots The Astrophysical Journal Magnetohydrodynamical simulations Solar coronal waves Alfvén waves Sunspots |
| title | The Coronal Power Spectrum from MHD Mode Conversion above Sunspots |
| title_full | The Coronal Power Spectrum from MHD Mode Conversion above Sunspots |
| title_fullStr | The Coronal Power Spectrum from MHD Mode Conversion above Sunspots |
| title_full_unstemmed | The Coronal Power Spectrum from MHD Mode Conversion above Sunspots |
| title_short | The Coronal Power Spectrum from MHD Mode Conversion above Sunspots |
| title_sort | coronal power spectrum from mhd mode conversion above sunspots |
| topic | Magnetohydrodynamical simulations Solar coronal waves Alfvén waves Sunspots |
| url | https://doi.org/10.3847/1538-4357/ada26f |
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