Atmospheric electricity in the Saturnian system

The purpose of this project is a successful continuation of the research activity on atmospheric electricity at the gas giant Saturn and its biggest moon Titan by analyzing data from the Cassini/RPWS (Radio and Plasma Wave Science) instrument. Radio waves from lightning discharges at Saturn (shortly named "SEDs" for Saturn Electrostatic Discharges) occur together with prominent cloud features imaged by Cassini/ISS (Imaging Science Subsystem) in Saturn`s atmosphere. Many papers about SEDs have been published recently in refereed journals by the writer of this proposal. A new, not yet analyzed months-long lightning storm on Saturn has provided intriguing new data from which new findings can be expected. Combined observations of radio and optical emissions of Saturn lightning should lead to new clues about the morphology and frequency of occurrence of thunderstorms in Saturn`s atmosphere. The SED related cloud features have diameters of several thousand kilometers, and they can even be imaged by amateur astronomers from Earth. A statistical analysis of the recent and further SED storms with respect to burst duration and rates, intensity, and frequency spectrum will be performed. Unique high temporal resolution observations of SEDs will be investigated in detail and compared to terrestrial intracloud strokes. SEDs act as a natural tool to probe Saturn`s ionosphere, and the ionospheric peak electron density (an important parameter for scientists studying Saturn`s ionosphere) will be determined from the SED low frequency cutoff. The SEDs can be detected even when the storm is "over the horizon" by as much as 45 when viewed from Cassini. This peculiar bending of radio waves by the planet`s ionosphere needs to be studied in more detail and ray-tracing calculations are planned to be made. The first measurements of intense SEDs close to Saturn will allow us to evaluate if direction-finding is possible with short and bursty radio waves like SEDs. The polarization of SEDs will be studied in more detail for the new Cassini as well as the old Voyager SED observations, because the latter have never been analyzed systematically. The main target of this project is Saturn, but the search for lightning in the atmosphere of Saturn`s enigmatic moon Titan will also be continued. Some results of the research on Saturn lightning can be used (1) to compare SED observations of RPWS with Earth-based SED observations and (2) to provide input for a micro- and macro-physical modeling of thunderclouds and lightning in Saturn`s atmosphere.

The purpose of this project is a successful continuation of the research activity on atmospheric electricity at the gas giant Saturn and its biggest moon Titan by analyzing data from the Cassini/RPWS (Radio and Plasma Wave Science) instrument. Radio waves from lightning discharges at Saturn (shortly named "SEDs" for Saturn Electrostatic Discharges) occur together with prominent cloud features imaged by Cassini/ISS (Imaging Science Subsystem) in Saturn`s atmosphere. Many papers about SEDs have been published recently in refereed journals by the writer of this proposal. A new, not yet analyzed months-long lightning storm on Saturn has provided intriguing new data from which new findings can be expected. Combined observations of radio and optical emissions of Saturn lightning should lead to new clues about the morphology and frequency of occurrence of thunderstorms in Saturn`s atmosphere. The SED related cloud features have diameters of several thousand kilometers, and they can even be imaged by amateur astronomers from Earth. A statistical analysis of the recent and further SED storms with respect to burst duration and rates, intensity, and frequency spectrum will be performed. Unique high temporal resolution observations of SEDs will be investigated in detail and compared to terrestrial intracloud strokes. SEDs act as a natural tool to probe Saturn`s ionosphere, and the ionospheric peak electron density (an important parameter for scientists studying Saturn`s ionosphere) will be determined from the SED low frequency cutoff. The SEDs can be detected even when the storm is "over the horizon" by as much as 45 when viewed from Cassini. This peculiar bending of radio waves by the planet`s ionosphere needs to be studied in more detail and ray-tracing calculations are planned to be made. The first measurements of intense SEDs close to Saturn will allow us to evaluate if direction-finding is possible with short and bursty radio waves like SEDs. The polarization of SEDs will be studied in more detail for the new Cassini as well as the old Voyager SED observations, because the latter have never been analyzed systematically. The main target of this project is Saturn, but the search for lightning in the atmosphere of Saturn`s enigmatic moon Titan will also be continued. Some results of the research on Saturn lightning can be used (1) to compare SED observations of RPWS with Earth-based SED observations and (2) to provide input for a micro- and macro-physical modeling of thunderclouds and lightning in Saturn`s atmosphere.