Anomalous Changes in Ionospheric Parameters During the Preparation and Occurrence of the M8.8 Earthquake and a Series of Earthquakes With M ≥ 6 That Occurred Near the Kamchatka Peninsula From June to September 2025 According to the Data of Satellite Navigation Systems

Changes in the altitude profiles of the ionospheric electron density (Ne) and the total electron content (TEC) were detected using satellite navigation system data during the preparation and occurrence of a powerful M8.8 earthquake (July 29, 2025, UTC) and other strong earthquakes of M ≥ 6 that occurred near the Kamchatka Peninsula in June–September 2025. A 9–18% decrease in the ionospheric electron density was detected, occurred 1–5 days before the M8.8 earthquake. A gradual decrease in the total electron content (TEC) began 3 months before the earthquake, ceasing 15 days before the event. Using the Long Short-Term Memory and Autoencoder neural networks, anomalies were identified in the time series of normalized values of the total electron content (NTEC) of the ionosphere during the preparation of earthquakes of M ≥ 6 that occurred in June–September 2025 near the Kamchatka Peninsula. The pattern of the anomalous variations in ionospheric parameters identified in this research corresponds to the characteristics of ionospheric anomalies during the preparation and occurrence of strong seismic events presented in earlier works.