Electric field snapshot data from RPW-TDS. (a) PSD of the SBM1 regular snapshot waveforms. Each point in time corresponds to the PSD vs. frequency of a snapshot. Snapshots last around 60 ms, and one is captured every second. The spectrogram shows PSD in dB above the minimum power of each snapshot. The red line indicates the electron plasma frequency. The Type II radio burst extends above f_pe from the shock ramp towards the upstream region, covering the whole interval shown. (b) RPW-TDS/MAMP data product containing the maximum data point within a 7.8 ms interval of the absolute value of the electric field. (c)–(e) SBM1 snapshots containing Langmuir waves and electrostatic solitary waves, indicated by the red vertical lines in panel (b). (f)–(h) Frequency spectrogram of the SBM1 snapshots in panels (c)–(e). The black line indicates the electron plasma frequency. (i)–(k) PSD of the SBM1 snapshots in panels (c)–(e).