Direct observation of warping in the plasma sheet of Saturn

Abstract

The ENA images from the Ion Neutral CAmera (INCA) on the Cassini spacecraft are projected onto the noon‐midnight plane of Sun‐Saturn orbital coordinates, and a composite “image” of Saturn's plasma sheet is constructed from dawn‐side observations of 20–50 keV hydrogens obtained from days 352 to 361 in 2004. The maxima in the intensity contours define the center of the plasma sheet in the noon‐midnight plane. This plasma sheet surface displays a distinct bending or “warping” above Saturn's equatorial plane at radial distances of beyond ∼15 RS on the nightside. On the dayside, the plasma sheet lies close to the equator all the way to the magnetopause. The observed warping agrees with the “bowl” model derived from measurements of Saturn's magnetic field, but fits more closely a simple third‐order polynomial.