Geophysical Research Letters

Are Saturn electrostatic discharges really superbolts? A temporal dilemma

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Abstract

[1] Saturn electrostatic discharges (SED) are freely-propagating radio emissions detected in the high frequency (HF) radio band (1–40 MHz) associated with electrical discharge (i.e., lightning) from storms in Saturn's atmosphere. While SEDs responsible for the RF emission are considered to be very energetic superbolts (>1013 J), this determination is intimately related to the temporal nature of the discharge itself. As we demonstrate, if we assume the discharge has similar temporal properties as terrestrial cloud-to-ground discharges (with a stroke time scale ∼70 μs), then indeed the discharge energy has to be ∼ 1013 J in order account for the Cassini-observed radiated HF power of ∼50 W/Hz. However, if the discharge duration is faster than the terrestrial case (i.e., ∼1 μs), the energy of the discharge can be weaker than the terrestrial case since the central peak of the emission shifts closer to the HF band. Because of the near-flat SED spectra measured in the HF which favors a faster discharge, we conclude that the high level of radiated HF power from SEDs may have less to do with any extreme super-bolt strength of the discharge and has more to do with the intrinsic quick time-scale of relatively weaker discharges.

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