Searching for low-altitude magnetic field anomalies by using observations of the energetic particle loss cone on JUNO

In inner planetary magnetospheres, pitch angle distributions of charged particles are shaped by the global magnetic field topology when they bounce fast along magnetic field lines. Therefore, one can estimate the magnetic field intensity at the top of the atmosphere from the loss cone size, inferred from particle pitch angle distributions at higher altitudes. We propose such a technique to estimate the magnetic field intensity near the top of Jovian atmosphere based on Jupiter Energetic Particle Detector Instruments particle distributions captured by JUNO and verify the algorithm by using plasma measurements from Van Allen Probes in the Earth's inner magnetosphere. Our results demonstrate that the low-altitude magnetic field can be significantly larger than the expected field from present models, which supports recent reports on the anomaly of Jovian internal magnetic field from in situ JUNO measurements. We also discuss possible modifications and applications of the proposed technique to future investigations of the global Jovian magnetic field configuration.