Buoyancy Modes in a Low Entropy Bubble

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dc.citation.articleNumbere2024JA032714en_US
dc.citation.issueNumber11en_US
dc.citation.journalTitleJournal of Geophysical Research: Space Physicsen_US
dc.citation.volumeNumber129en_US
dc.contributor.authorToffoletto, F. R.en_US
dc.contributor.authorWolf, R. A.en_US
dc.contributor.authorDerr, J.en_US
dc.date.accessioned2025-01-09T20:16:56Zen_US
dc.date.available2025-01-09T20:16:56Zen_US
dc.date.issued2024en_US
dc.description.abstractIn the nightside region of Earth's magnetosphere, braking oscillations or buoyancy modes have been associated with the occurrence of low entropy bubbles. These bubbles form in the plasma sheet, particularly during geomagnetically disturbed times, and because of interchange, move rapidly earthward and may eventually come to rest in the inner plasma sheet or inner magnetosphere. Upon arrival, they often exhibit damped oscillations with periods of a few minutes and are associated with Pi2 pulsations. Previously we used the thin filament approximation to compare the frequencies and modes of buoyancy waves using magnetohydrodynamic (MHD) ballooning and classic interchange theory. Interchange oscillations differ from the more general MHD oscillations by assuming constant pressure along a magnetic field line. It was determined that MHD ballooning and interchange modes are similar for plasma sheet field lines but differ for field lines that map to the inner magnetosphere. This suggested that the classic interchange formulation was only valid in the plasma sheet. This paper tests the hypothesis that the agreement between MHD ballooning and classic interchange could be restored inside a bubble. We create a small region of entropy depletion in the magnetotail and compare the buoyancy mode properties. At some locations inside the bubble, the MHD ballooning buoyancy modes resemble interchange modes but with lower frequencies than those of the unperturbed background. Unstable modes are found on the earthward edge of the bubble, while at the tailward edge, MHD ballooning predicts a slow mode wave solution not seen in the pure interchange solution.en_US
dc.identifier.citationToffoletto, F. R., Wolf, R. A., & Derr, J. (2024). Buoyancy Modes in a Low Entropy Bubble. Journal of Geophysical Research: Space Physics, 129(11), e2024JA032714. https://doi.org/10.1029/2024JA032714en_US
dc.identifier.digitalBuoyancyModesLowEntropyBubbleen_US
dc.identifier.doihttps://doi.org/10.1029/2024JA032714en_US
dc.identifier.urihttps://hdl.handle.net/1911/118098en_US
dc.language.isoengen_US
dc.publisherWileyen_US
dc.rightsExcept where otherwise noted, this work is licensed under a Creative Commons Attribution (CC BY) license. Permission to reuse, publish, or reproduce the work beyond the terms of the license or beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.en_US
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/en_US
dc.titleBuoyancy Modes in a Low Entropy Bubbleen_US
dc.typeJournal articleen_US
dc.type.dcmiTexten_US
dc.type.publicationpublisher versionen_US
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