DOI: 10.1029/2017JA025006
Scopus记录号: 2-s2.0-85046700462
论文题名: Buoyancy Waves in Earth's Magnetosphere: Calculations for a 2-D Wedge Magnetosphere
作者: Wolf R.A. ; Toffoletto F.R. ; Schutza A.M. ; Yang J.
刊名: Journal of Geophysical Research: Space Physics
ISSN: 21699380
出版年: 2018
卷: 123, 期: 5 起始页码: 3548
结束页码: 3564
语种: 英语
英文关键词: braking oscillations
; bursty bulk flows
; magnetic buoyancy
; ULF waves
英文摘要: To improve theoretical understanding of the braking oscillations observed in Earth's inner plasma sheet, we have derived a theoretical model that describes k∥ = 0 magnetohydrodynamic waves in an idealized magnetospheric configuration that consists of a 2-D wedge with circular-arc field lines. The low-frequency, short-perpendicular-wavelength mode obeys a differential equation that is often used to describe buoyancy oscillations in a neutral atmosphere, so we call those waves “buoyancy waves,” though the magnetospheric buoyancy force results from magnetic tension rather than gravity. Propagation of the wave is governed mainly by a position-dependent frequency ωb, the “buoyancy frequency,” which is a fundamental property of the magnetosphere. The waves propagate if ωb > ω but otherwise evanesce. In the wedge magnetosphere, ωb turns out to be exactly the fundamental oscillation frequency for poloidal oscillations of a thin magnetic filament, and we assume that the same is true for the real magnetosphere. Observable properties of buoyancy oscillations are discussed, but propagation characteristics vary considerably with the state of the magnetosphere. For a given event, the buoyancy frequency and propagation characteristics can be determined from pressure and density profiles and a magnetic field model, and these characteristics have been worked out for one typical configuration. A localized disturbance that initially resembles a dipolarizing flux bundle spreads east-west and also penetrates into the plasmasphere to some extent. The calculated amplitude near the center of the original wave packet decays in a few oscillation periods, even though our calculation includes no dissipation. ©2018. American Geophysical Union. All Rights Reserved. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/113944
Appears in Collections: 气候减缓与适应
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作者单位: Physics and Astronomy Department, Rice University, Houston, TX, United States
Recommended Citation:
Wolf R.A.,Toffoletto F.R.,Schutza A.M.,et al. Buoyancy Waves in Earth's Magnetosphere: Calculations for a 2-D Wedge Magnetosphere[J]. Journal of Geophysical Research: Space Physics,2018-01-01,123(5)