A Complete Data Set of Equatorial Projections of Saturn's Energetic Neutral Atom Emissions Observed by Cassini‐INCA

Abstract

Energetic neutral atom (ENA) imaging is a useful technique for analyzing the interaction between hot space plasmas and neutral gas in planetary magnetospheres. Energetic ions can undergo charge exchange with a neutral population -the planetary exosphere, for example -to create an ENA particle that carries information on the original ion's energy and direction of motion. This ENA continues on its trajectory, unaffected by electromagnetic fields, and can be observed by a remote detector. Remote sensing of an ENA population hence provides spectral, compositional, and pitch angle information of the source plasma. As the observed

The Statistical Morphology of Saturn’s Equatorial Energetic Neutral Atom Emission

“…The emissions are observed across four imaging bands; low and high energy hydrogen-derived ENAs (24-55 keV and 55-90 keV, respectively), and low and high energy oxygen (90-170 keV and 170-230 keV, respectively). We have used a new algorithm to sort, calibrate and project this ENA imagery into the equatorial plane for analysis, documented in Bader, Kinrade, et al (2021). The final processed images are based on up to hundreds of days of accumulative exposure in some regions of the magnetosphere.…”

“…Here we chose to only take into account measurements from spacecraft lineof-sight distances between 5 and 30 R S from a given pixel, and from spacecraft elevations between 50° and 90° above a given pixel. Projections showing signs of data contamination (from sunlight or ion leakage in neutral imaging mode) were identified in Bader, Kinrade, et al (2021) and excluded from this study.…”

“…We countered this difficulty by projecting all observations into Saturn's equatorial plane where most ENAs are created due to increased ion and neutral densities. The processing steps and the newly created data set are described in more detail in a dedicated technical report by Bader, Kinrade, et al (2021). Characterization of the vertical ENA emission structure away from the magnetic/spin equator requires the use of a different projection routine and remains a possibility for future work.…”

“…Mean intensities are then calculated using the number of observations in each histogram bin. As described in detail in Bader, Kinrade, et al (2021), many projections are unsuitable for use as the viewing geometry under which they were obtained leads to pixel stretching or significant loss of resolution. Here we chose to only take into account measurements from spacecraft lineof-sight distances between 5 and 30 R S from a given pixel, and from spacecraft elevations between 50° and 90° above a given pixel.…”

“…The processing steps and the newly created data set are described in more detail in a dedicated technical report by Bader, Kinrade, et al. (2021). Characterization of the vertical ENA emission structure away from the magnetic/spin equator requires the use of a different projection routine and remains a possibility for future work.…”