The Saturnian Kilometric Radiation before the Cassini Grand Finale

TL;DR

This paper reviews the understanding of Saturnian Kilometric Radiation (SKR) before the Cassini Grand Finale, highlighting remote and in situ observations, and discussing remaining questions about its properties and source regions.

Contribution

It provides a comprehensive review of SKR observations and insights gained from Cassini's in situ measurements prior to the Grand Finale.

Findings

SKR is emitted from Saturn's auroral regions.

Cassini provided in situ data on SKR source regions.

Remaining questions about SKR's detailed properties.

Abstract

The Saturnian Kilometric Radiation (SKR) is radiated from the auroral regions surrounding the kronian magnetic poles, above the ionosphere up to a few planetary radii. It directly compares to the auroral radio emissions emanating from other planetary magnetospheres such as the Earth and the giant planets. Our knowledge on SKR relied on remote observations of Voyager (flybys in 1980 and 1981) and Ulysses (distant observations in the 1990s) until Cassini started to orbit Saturn in 2004. Since then, it has been routinely observed from a large set of remote locations, but also in situ for the first time at a planet other than Earth. This article reviews the state of the art of SKR average remote properties, the first insights brought by in situ passes within its source region, together with some remaining questions before the Cassini Grand Finale and its close-in polar orbits.