globalchange  > 气候减缓与适应
DOI: 10.1002/2017JA024713
Scopus记录号: 2-s2.0-85040654719
论文题名:
Diagnosing the Role of Alfvén Waves in Magnetosphere-Ionosphere Coupling: Swarm Observations of Large Amplitude Nonstationary Magnetic Perturbations During an Interval of Northward IMF
作者: Pakhotin I.P.; Mann I.R.; Lysak R.L.; Knudsen D.J.; Gjerloev J.W.; Rae I.J.; Forsyth C.; Murphy K.R.; Miles D.M.; Ozeke L.G.; Balasis G.
刊名: Journal of Geophysical Research: Space Physics
ISSN: 21699380
出版年: 2018
卷: 123, 期:1
起始页码: 326
结束页码: 340
语种: 英语
英文关键词: Alfvén waves ; Birkeland currents ; ionosphere ; magnetosphere ; magnetosphere-ionosphere interaction ; wave reflection
英文摘要: High-resolution multispacecraft Swarm data are used to examine magnetosphere-ionosphere coupling during a period of northward interplanetary magnetic field (IMF) on 31 May 2014. The observations reveal a prevalence of unexpectedly large amplitude (>100 nT) and time-varying magnetic perturbations during the polar passes, with especially large amplitude magnetic perturbations being associated with large-scale downward field-aligned currents. Differences between the magnetic field measurements sampled at 50 Hz from Swarm A and C, approximately 10 s apart along track, and the correspondence between the observed electric and magnetic fields at 16 samples per second, provide significant evidence for an important role for Alfvén waves in magnetosphere-ionosphere coupling even during northward IMF conditions. Spectral comparison between the wave E- and B-fields reveals a frequency-dependent phase difference and amplitude ratio consistent with interference between incident and reflected Alfvén waves. At low frequencies, the E/B ratio is in phase with an amplitude determined by the Pedersen conductance. At higher frequencies, the amplitude and phase change as a function of frequency in good agreement with an ionospheric Alfvén resonator model including Pedersen conductance effects. Indeed, within this Alfvén wave incidence, reflection, and interference paradigm, even quasi-static field-aligned currents might be reasonably interpreted as very low frequency (ω → 0) Alfvén waves. Overall, our results not only indicate the importance of Alfvén waves for magnetosphere-ionosphere coupling but also demonstrate a method for using Swarm data for the innovative experimental diagnosis of Pedersen conductance from low-Earth orbit satellite measurements. ©2018. The Authors.
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资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/114772
Appears in Collections:气候减缓与适应

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作者单位: Department of Physics, University of Alberta, Edmonton, AB, Canada; School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, United States; University of Calgary, Calgary, AB, Canada; Johns Hopkins University Applied Physics Laboratory, Laurel, MD, United States; Mullard Space Science Laboratory, University College London, London, United Kingdom; NASA Goddard Space Flight Center, Greenbelt, MD, United States; Department of Physics and Astronomy, University of Iowa, Iowa City, IA, United States; National Observatory of Athens, Athens, Greece

Recommended Citation:
Pakhotin I.P.,Mann I.R.,Lysak R.L.,et al. Diagnosing the Role of Alfvén Waves in Magnetosphere-Ionosphere Coupling: Swarm Observations of Large Amplitude Nonstationary Magnetic Perturbations During an Interval of Northward IMF[J]. Journal of Geophysical Research: Space Physics,2018-01-01,123(1)
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