Saturn Magnetospheric Power Budget: Rotational Energy Supply, Solar Wind Input and Auroral Output Compared from Cassini Measurements

This paper computes a quantitative budget for the magnetosphere of Saturn from published spacecraft values, using a deliberately transparent calculation whose every step can be checked from the deposited script. The headline results are: rotational_energy_J = 5.69e+33; auroral_power_W = 1e+11; solar_wind_intercepted_power_W = 5e+11; auroral_to_solar_wind_ratio = 0.2; rotation_drain_time_Gyr = 1.8e+06. The auroral output is a modest fraction of the intercepted solar wind power and an utterly negligible drain on rotation, whose reservoir would sustain the present aurora for far longer than the age of the Solar System. The budget therefore cannot decide Saturn's engine by exhaustion arguments; it decides it by coupling, and the observed dependence of Saturn's aurora and kilometric radiation on both rotation phase and solar wind conditions matches the intermediate position the numbers suggest, with internal plasma loading mediating between the two supplies. 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.