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Are Saturn electrostatic discharges really superbolts? A temporal dilemma

Abstract : 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 mus), 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 mus), 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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William M. Farrell, Michael L. Kaiser, Georg Fischer, Philippe Zarka, William S. Kurth, et al.. Are Saturn electrostatic discharges really superbolts? A temporal dilemma. Geophysical Research Letters, American Geophysical Union, 2007, 34, pp.06202. ⟨10.1029/2006GL028841⟩. ⟨hal-03742728⟩



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