How a realistic magnetosphere alters the polarizations of surface, fast magnetosonic, and Alfvén waves

M. O. Archer*, D. J. Southwood, M. D. Hartinger, L. Rastaetter, A. N. Wright

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


System-scale magnetohydrodynamic (MHD) waves within Earth?s magnetosphere are often understood theoretically using box models. While these have been highly instructive in understanding many fundamental features of the various wave modes present, they neglect the complexities of geospace such as the inhomogeneities and curvilinear geometries present. Here we show global MHD simulations of resonant waves impulsively-excited by a solar wind pressure pulse. Although many aspects of the surface, fast magnetosonic (cavity/waveguide), and Alfvén modes present agree with the box and axially symmetric dipole models, we find some predictions for large-scale waves are significantly altered in a realistic magnetosphere. The radial ordering of fast mode turning points and Alfvén resonant locations may be reversed even with monotonic wave speeds. Additional nodes along field lines that are not present in the displacement/velocity occur in both the perpendicular and compressional components of the magnetic field. Close to the magnetopause the perpendicular oscillations of the magnetic field have the opposite handedness to the velocity. Finally, widely-used detection techniques for standing waves, both across and along the field, can fail to identify their presence. We explain how all these features arise from the MHD equations when accounting for a non-uniform background field and propose modified methods which might be applied to spacecraft observations.
Original languageEnglish
Article numbere2021JA030032
Number of pages23
JournalJournal of Geophysical Research: Space Physics
Issue number2
Early online date7 Feb 2022
Publication statusPublished - Feb 2022


  • Ulf waves
  • Polarization
  • Magnetohydrodynamics
  • Simulation
  • Theory


Dive into the research topics of 'How a realistic magnetosphere alters the polarizations of surface, fast magnetosonic, and Alfvén waves'. Together they form a unique fingerprint.

Cite this