Extended Data Table 1 Discharge parameters inferred from the sound signal characteristics

From: Detection of triboelectric discharges during dust events on Mars

  1. The sound speed is computed using the atmospheric temperature at 1.45 m from the ground retrieved by MEDA at the time of the closest measurement available from the event. The error on the sound speed is computed using the standard deviation of the atmospheric temperature. The propagation time is taken as the time delay between the electromagnetic overshoot and the acoustic wave. In the case of close-distance discharges, the propagation time corresponds to only several samplings (the time resolution is 4 × 10−2 for the sampling frequency of 25 kHz). The amplitude of the sound wave is computed after removing the electronics response baseline. The distance of the discharge is deduced using its propagation time over the sound speed. The sound’s path difference is computed as the sound speed over frequency gap. It corresponds to the extra distance travelled by the reflected acoustic wave on the structure around the microphone. A variation in that distance implies a varying incoming direction of the direct acoustic wave. For events 317a and 871, no echo can be observed on the time series. The energy of the discharge is obtained using the weak shock-wave propagation model (Methods section ‘Discharge energy estimation’).
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