Exploring Jupiter's Polar Deformation Lengths with High-resolution Shallow Water Modeling

Abstract

The polar regions of Jupiter host a myriad of dynamically interesting phenomena, including vortex configurations, folded-filamentary regions (FFRs), and chaotic flows. Juno observations have provided unprecedented views of the high latitudes, allowing for more constraints to be placed upon the troposphere and the overall atmospheric energy cycle. Moist convective events are believed to be the primary drivers of energetic storm behavior as observed on the planet. Here we introduce a novel single-layer shallow water model to investigate the effects of polar moist convective events at high resolution, the presence of dynamical instabilities over long timescales, and the emergence of FFRs at high latitudes. We use a flexible, highly parallelizable, finite difference hydrodynamic code to explore the parameter space set up by previous models. We study the long-term effects of deformation length (L d ), injected pulse size, and injected geopotential. We find that models with L d beyond 1500 km (planetary Burger number, Bu = 4.4 × 10−4) tend to homogenize their potential vorticity in the form of dominant stable polar cyclones, while lower-L d cases tend to show less stability with regard to Arnol’d-type flows. We also find that large turbulent forcing scales consistently lead to the formation of high-latitude FFRs. Our findings support the idea that moist convection occurring at high latitudes may be sufficient to produce the dynamical variety seen at the Jovian poles. Additionally, derived values of localized horizontal shear and L d may constrain FFR formation and evolution.

The Westward Drift of Jupiter's Polar Cyclones Explained by a Center‐of‐Mass Approach

“…where R J is the radius of Jupiter, θ is latitude and λ is longitude. The planetary radius here, calculated as R J = R 2 e/Rp = 76, 452 km 18 , is the osculating radius, taking Jupiter's oblateness into account. This data, per PJ, is temporally interpolated separately for the x and y coordinates.…”

“…While a stable configuration of CPCs was never observed before Juno's polar approaches, a PC has been persistently observed at each pole of Saturn (Baines et al., 2009). The formation of a PC on a gas giant is well understood and revolves around the concept of “beta‐drift,” which drives cyclonic vortices poleward (Adem, 1956; Fiorino & Elsberry, 1989; Rossby, 1948; Smith & Ulrich, 1990), where they converge and maintain a PC (Brueshaber et al., 2019; Hyder et al., 2022; O’Neill et al., 2015, 2016; Scott, 2011). This β ‐drift mechanism will be further explained in the following sections.…”

“…While a stable configuration of CPCs were never observed before Juno's polar approaches, a polar cyclone has been persistently observed at each pole of Saturn 9 . The formation of a polar cyclone on a gas giant is well understood and revolves around the concept of "beta-drift", which drives cyclonic vortices poleward 10,11,12,13 , where they converge and maintain a polar cyclone 14,15,16,17,18 . This β -drift mechanism will be further explained in the following sections.…”