![]() ![]() ![]() Magnetospheric ultra-low frequency (ULF) waves are categorized by continuous pulsations in five consecutive ranges 1–5 ( Jacobs et al., 1964). The terrestrial magnetosphere contains a rich variety of low-frequency fluctuations. The EMIC wave occurrence is strongly related to pressure anisotropy and β ‖, both vary as a function of the upstream conditions, whereas the mirror mode occurrence is highly influenced by fast waves generated from upstream density variations. Less prominent EMIC and mirror mode wave activities near the center of magnetosheath are observed with decreasing upstream Mach number. We characterize the spatial-temporal properties of ULF waves at different phases of the variation. ![]() The oscillations also create large-scale stripes of variations in the magnetosheath and modulate the mirror and electromagnetic ion cyclotron modes. A breathing motion of the magnetopause and changes in the bow shock standoff position are caused by the density variation, the time lag between which is found to be consistent with propagation at fast magnetohydrodynamic speed. With the new time-varying boundary setup, we introduce a monochromatic Pc5 range periodic density variation in the solar wind. Here we investigate the influence of externally-driven density variations in the near-Earth space in the ULF regime using global 2D simulations performed with the hybrid-Vlasov model Vlasiator. Ultra-low frequency (ULF) waves are routinely observed in Earth’s dayside magnetosphere.
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