Schumann resonance frequency remains outside its quiet-time range for days after geomagnetic recovery at a mid-latitude station (2013–2017) — Option F frozen archive

Geomagnetic storms disturb the Schumann resonances, but how long the disturbance lasts after geomagnetic activity has calmed is unclear. We timed 42 storm episodes (Kp ≥ 6−, March 2013–February 2017) from the point at which Kp recovered to ≤ 4+ for at least 6 h. We then measured how long the first-mode frequency on the north–south coil of the Sierra Nevada ELF station (Spain) stayed outside its quiet-day 95% band, and compared it with local ionospheric TEC. Two independent pipelines agree that the frequency stays disturbed for about 2–5 days. In pipeline A the Kaplan–Meier median was 79 h (n = 41). In pipeline B the median of observed and censored times was 69 h and the Kaplan–Meier median was not reached within 120 h (n = 39). The early deviation was significant for frequency (Holm-adjusted p = 3.1 × 10⁻⁴) but not for TEC, and TEC recovered sooner (Kaplan–Meier median 58–61 h). These results describe one station and show association, not cause; global lightning variability is a plausible alternative explanation. We release the derived hourly parameters, the episode catalogue and the code. Frozen derived archive (Option F): hourly and 10-minute Lorentzian-fit Schumann resonance parameters (Sierra Nevada ELF station, NS/EW coils), quiet-day series, Kp-recovery episode catalogue and quiet-day lists, CODE vertical TEC series, provenance/checksum tables for the third-party raw ELF records, results tables/figures, and the analysis code. Raw ELF records (~100 GB) are NOT included; they are the third-party CC BY 4.0 Zenodo records 10.5281/zenodo.6348930, .6348691, .6348773, .6348838 (Salinas et al.). SHA-256 checksums in SHA256SUMS. Data and text: CC BY 4.0. Code in code/ is MIT-licensed (see LICENSE / code/LICENSE).