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Solar wind ram pressure7/22/2023 ![]() However, the details of the interaction of solar wind variations with the Earth’s bow shock and magnetosheath, their impact on the magnetosheath plasma properties and how the fluctuations would change before reaching the magnetopause especially on the global scale, remain unclear. This in turn modifies plasma convection ( Motoba et al., 2007), generates plasma oscillations inside the magnetosphere ( Kepko et al., 2002 Kepko and Viall, 2019 Di Matteo et al., 2022) and possibly causes sunward flows in the magnetosheath ( Archer et al., 2014). Pressure variations in the solar wind can trigger fast shock and fast rarefaction waves downstream of the bow shock ( Wu et al., 1993) and result in a forced breathing of the magnetosphere, as the magnetopause expands and shrinks in response to the changing upstream conditions. One important source of magnetospheric Pc5 waves are fluctuations of the upstream solar wind parameters in the same frequency range, e.g. ULF waves in the Pc5 range 150–600 s play a key role in the dynamics of Earth’s magnetosphere, in particular through their interaction with radiation belt electrons ( Elkington, 2006 Zong et al., 2017 Ripoll et al., 2020), modulation of particle precipitation ( Wang et al., 2020), total electron content ( Kozyreva et al., 2020), geomagnetically induced currents ( Heyns et al., 2021) and contribution to magnetosphere-ionosphere coupling via Joule heating and/or ion frictional heating with neutrals ( Hartinger et al., 2015 Baddeley et al., 2017). 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. 3Finnish Meteorological Institute, Helsinki, Finland.2Swedish Institute of Space Physics, Uppsala, Sweden.1University of Helsinki, Helsinki, Finland.Hongyang Zhou 1*, Lucile Turc 1, Yann Pfau-Kempf 1, Markus Battarbee 1, Vertti Tarvus 1, Maxime Dubart 1, Harriet George 1, Giulia Cozzani 1, Maxime Grandin 1, Urs Ganse 1, Markku Alho 1, Andreas Johlander 2, Jonas Suni 1, Maarja Bussov 1, Konstantinos Papadakis 1, Konstantinos Horaites 1, Ivan Zaitsev 1, Fasil Tesema 1, Evgeny Gordeev 1 and Minna Palmroth 1,3 ![]()
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