Analysis of a giant lightning storm on Saturn |
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Authors: | G Fischer WS Kurth ML Kaiser A Lecacheux DA Gurnett |
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Institution: | a Department of Physics and Astronomy, University of Iowa, 203 Van Allen Hall, Iowa City, IA 52242, USA b 150-21 Geological and Planetary Sciences, Caltech, Pasadena, CA 91125, USA c NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771, USA d Observatoire de Paris-Meudon, 5 Place Jules Janssen, 92195 Meudon Cedex, France |
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Abstract: | On January 23, 2006, the Cassini/RPWS (Radio and Plasma Wave Science) instrument detected a massive outbreak of SEDs (Saturn Electrostatic Discharges). The following SED storm lasted for about one month and consisted of 71 consecutive episodes. It exceeded all other previous SED observations by Cassini as well as by the Voyagers with regard to number and rate of detected events. At the same time astronomers at the Earth as well as Cassini/ISS (Imaging Science Subsystem) detected a distinctive bright atmospheric cloud feature at a latitude of 35° South, strongly confirming the current interpretation of SEDs being the radio signatures of lightning flashes in Saturn's atmosphere. In this paper we will analyze the main physical properties of this SED storm and of a single small SED storm from 2005. The giant SED storm of 2006 had maximum burst rates of 1 SED every 2 s, its episodes lasted for 5.5 h on average, and the episode's periodicity of about 10.66 h exactly matched the period of the ISS observed cloud feature. Using the low frequency cutoff of SED episodes we determined an ionospheric electron density around 104 cm−3 for the dawn side of Saturn. |
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Keywords: | Saturn Lightning Saturn atmosphere Radio observations |
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