Ring Seismology of the Ice Giants Uranus and Neptune

We assess the prospect of using ring seismology to probe the interiors of the ice giants Uranus and Neptune. We do this by calculating normal-mode spectra for different interior models of Uranus and Neptune using the stellar oscillation code GYRE. These spectra provide predictions of where in these planets' ring systems the effects of interior oscillations might be detected. We find that f-mode resonances with azimuthal order m = 2 or 7 <= m <= 19 fall among the inner rings (6, 5, 4, alpha, and beta) of Uranus, while f-mode resonances with 2 <= m <= 12 fall in the tenuous zeta ring region. In addition, f-mode resonances with m = 2 or 6 <= m <= 13 may give azimuthal structure to Neptune's tenuous Galle ring. We also find that g-mode resonances may fall in the middle to outer rings of these planets. Although an orbiter is most likely required to confirm the association between any waves in the rings and planetary normal modes, the diversity of normal-mode spectra implies that identification of just one or two modes in the rings of Uranus or Neptune would eliminate a variety of interior models and thus aid in the interpretation of Voyager observations and future spacecraft measurements.

Automated summary

In this study, we assess the potential of using ring seismology to investigate the interiors of Uranus and Neptune. By calculating normal-mode spectra for different interior models of these planets, we determine the regions in their ring systems where the effects of interior oscillations can be detected. We find that certain resonances occur within the rings of Uranus, while others are present in the tenuous ring region of Neptune. Additionally, g-mode resonances may be found in the outer rings of these planets.