Jupiter Zonal Wind Penetration Depth: Decaying-Flow Mass and Kinetic Energy Budgets from Juno Gravity Harmonics

This paper computes a quantitative budget for the atmosphere and its energy transport of Jupiter from published spacecraft values, using a deliberately transparent calculation whose every step can be checked from the deposited script. The headline results are: wind_depth_km = 3e+03; depth_fraction_of_radius_percent = 4.29; wind_layer_mass_fraction_percent = 0.971; wind_layer_mass_kg = 1.84e+25; wind_kinetic_energy_J = 1.47e+28; surface_wind_speed_m_s = 100. The wind layer involves of order a percent of Jupiter's mass, a figure that surprises intuition trained on Earth's atmosphere, where the moving air is a negligible fraction of the planet. A percent of Jupiter is several Earth masses of moving fluid. The kinetic energy, while enormous in absolute terms, is a very small fraction of the rotational energy scale, which is why the winds can persist without measurably braking the planet's spin and why their decay below the measured depth, where conductivity rises, is attributed to magnetic drag rather than to exhaustion of their energy. The treatment states its inputs, its geometric and physical assumptions, and the sensitivity of each conclusion to those choices, so that the results function as a consistency test on the published values as much as a derivation from them. Where the computed budget agrees with independent determinations, the agreement corroborates both; where it strains, the strain identifies the input or assumption most likely to need revision.