CLIMATIC CHANGES IN THE UPPER IONOSPHERE: LONG-TERM VARIATIONS AND TRENDS IN THE CRITICAL FREQUENCY OF THE F2 LAYER IN THE KAZAKHSTAN REGION. ЖПЭОС [Internet]. 2025 Jun. 30 [cited 2026 Jul. 13];27(1):35-48. Available from: https://peos.kaznu.kz/index.php/peos/article/view/342