Fig. 1: Coordinated observations of PSW and associated SA on 16 July 2017.

a Schematic diagram showing the geometry of the plasmasphere (deep green area), the auroral boundary (white thick curve), and spacecraft trajectories (VAP-A, VAP-B, and ERG spacecraft shown in blue, red, and pink, respectively) on the equatorial plane in the solar magnetic (SM) coordinate system with the Sun to the left (see the Methods section, coordinate system). The shape of the plasmapause is calculated from an empirical plasmaspheric model³⁷. The clear sawtooth-shaped plasmapause structure visible in the afternoon-dusk sector indicates the PSW, which is manually added based on the wavelength of the PSW calculated in the main text. The closed circles in the spacecraft trajectories indicate temporal intervals of 1 h beginning at 13:00 UTC (indicated by the leftmost circles overlaid with crosses). Both VAP-A and VAP-B spacecraft were located in the southern hemisphere while ERG spacecraft crossed the magnetic equator at ~14:10 UTC. Open diamonds represent the plasmapause crossings by the spacecraft. Note that VAP-A and VAP-B crossed the plasmapause region roughly azimuthally while ERG crossed almost radially. b SA observed by DMSP F17 in the Northern Hemisphere (NH) at 13:27:45 UTC. c SA observed by DMSP F17 in the SH at 14:37:13 UTC. The dashed grid lines in b, c denote the altitude-adjusted corrected geomagnetic (AACGM)³⁸ latitudes and magnetic local time (MLT). The thick dotted line in c represents the boundary of the SA, which is projected onto the SM equatorial plane using the Tsyganenko 96 magnetic field model³⁶ and denoted by the white curve at the duskside plasmapause in (a). d Spectrogram of the electric field from the high frequency receiver of the EMFISIS instrument suite onboard VAP-A. The next two panels show the energy spectrograms of electrons e and protons f measured by the HOPE mass spectrometer onboard VAP-A, respectively. The plasmaspheric electron density (blue curve) is overlaid on (e, f). g–i The same as those of d–f but for the ERG spacecraft. Details of the instruments and data availability can be found in Methods (see the Methods section, data usage).