The effect of fast normal mode structure and magnetopause forcing on FLRs in a 3‐D waveguide
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This paper investigates the excitation of waveguide modes in a nonuniform dipole equilibrium and, further, their coupling to field line resonances (FLRs). Waveguide modes are fast compressional ultralow frequency (ULF) waves, whose structure depends upon the magnetospheric equilibrium and the solar wind driving conditions. Using magnetohydrodynamic simulations, we consider how the structure of the excited waveguide mode is affected by various forms of magnetopause driving. We find that the waveguide supports a set of normal modes that are determined by the equilibrium. However, the particular normal modes that are excited are determined by the structure of the magnetopause driver. A full understanding of the spatial structure of the normal modes is required in order to predict where coupling to FLRs will occur. We show that symmetric pressure driving about the noon meridian can excite normal modes which remain around to drive resonances for longer than antisymmetric driving. Further, the critical quantity in terms of efficient coupling is the magnetic pressure gradient aligned with the resonance.
Elsden , T & Wright , A N 2019 , ' The effect of fast normal mode structure and magnetopause forcing on FLRs in a 3‐D waveguide ' , Journal of Geophysical Research: Space Physics , vol. 124 , no. 1 , pp. 178-196 . https://doi.org/10.1029/2018JA026222
Journal of Geophysical Research: Space Physics
© 2018, American Geophysical Union. This work has been made available online in accordance with the publisher's policies. This is the final published version of the work, which was originally published at https://doi.org/10.1029/2018JA026222
DescriptionT. Elsden and A. N. Wright were funded by the Leverhulme Trust through Research grant RPG-2016-071. A. N. Wright was also funded by STFC through Consolidated grant ST/N000609/1.
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