Detection of lightning in Saturn's Northern Hemisphere

TL;DR

This study detects and analyzes whistler signals from lightning in Saturn's northern hemisphere using Cassini data, estimating ion composition and scale height to understand Saturn's atmospheric electrical activity.

Contribution

It presents the first detection of Saturnian lightning via whistler signals and models ion composition and scale height from dispersion data.

Findings

Detected whistler signals consistent with lightning in Saturn's northern hemisphere

Estimated ion composition and scale height from dispersion characteristics

Confirmed lightning origin through travel time analysis

Abstract

During Cassini flyby of Saturn at a radial distance 6.18R_s (Saturn Radius), a signal was detected from about 200 to 430 Hz that had the proper dispersion characteristics to be a whistler. The frequency-time dispersion of the whistler was found to be 81 Hz1/2s. Based on this dispersion constant, we determined, from a travel time computation, that the whistler must have originated from lightning in the northern hemisphere of Saturn. Using a simple centrifugal potential model consisting of water group ions, and hydrogen ions we also determine the fractional concentration and scale height that gave the best fit to the observed dispersion.