A Jupiter System III–Locked Modulation in Global Ground Magnetometer Data

We report evidence for an nT-scale component in ground magnetometer data that is phase-locked to Jupiter’s System III rotation. Using multi-year INTERMAGNET stations, ephemeris-locked mixing, surrogate/null tests, and cross-index gating (AE/Dst/Kp), we find a persistent spectral envelope consistent with a System III reference. We include full reproducibility notes, checksums, and four supplements (A1–A4). Licensing: Text/figures CC BY 4.0. Code/scripts Apache-2.0 (see LICENSE in the ZIP).Data citation: INTERMAGNET; WDC Kyoto AE/Dst (DOIs: 10.17593/15031-54800, 10.17593/14515-74000); GFZ Kp (DOI: 10.5880/Kp.0001); NASA/JPL HORIZONS (Giorgini et al., 1996).ORCID: https://orcid.org/0009-0003-5655-0052