Solnechno-Zemnaya Fizika Solnechno-Zemnaya Fizika Солнечно-земная физика 2712-9640 109010 10.12737/szf-114202505 Результаты исследований Results of current research Результаты исследований Trends in the F2-layer critical frequency from data obtained at the ionospheric station Yakutsk during the period from 1956 to 2017 Тренды критической частоты слоя F2 по данным ионосферной станции «Якутск» за период с 1956 по 2017 г. Кобякова Саргылана Егоровна Kobyakova Sargylana Egorovna s.e.kobyakova@ikfia.ysn.ru https://orcid.org/0000-0003-2184-8089 Гололобов Артем Юрьевич Gololobov Artem Yuryevich golart87@gmail.com

кандидат физико-математических наук;

candidate of physical and mathematical sciences;

 Каримов Рустам Рамильевич Karimov Rustam Ramilyevich karimov@ikfia.ysn.ru

кандидат физико-математических наук;

candidate of physical and mathematical sciences;

 Степанов Александр Егорович Stepanov Aleksandr Egorovich a_e_stepanov@ikfia.ysn.ru Институт космофизических исследований и аэрономии им. Ю.Г. Шафера СО РАН Якутск Россия Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy SB RAS Yakutsk Russian Federation Институт космофизических исследований и аэрономии им. Ю.Г. Шафера СО РАН Якутск Россия Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy SB RAS Yakutsk Russian Federation Северо-Восточный федеральный университет им. М.К. Аммосова Якутск Россия North-Eastern Federal University Yakutsk Russian Federation Институт космофизических исследований и аэрономии им. Ю.Г. Шафера СО РАН Якутск Россия Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy of SB RAS Yakutsk Russian Federation Институт космофизических исследований и аэрономии им. Ю.Г. Шафера СО РАН Якутск Россия Yu.G. Shafer Institute of Cosmophysical Research and Aeronomy SB RAS Yakutsk Russian Federation 10 12 2025 10 12 2025 11 4 55 63 25 03 2025 20 08 2025 https://zh-szf.ru/en/nauka/article/109010/view

Проведен статистический анализ данных вертикального зондирования ионосферы на станции «Якутск» (62.01° N, 129.43° E, 57.12° MLAT) за период с 1956 по 2017 г., включающий шесть циклов солнечной активности, с целью выявления долговременных изменений в слое F2 субавроральной ионосферы, а также их связи с солнечной и геомагнитной активностью. Рассмотрены вариации одного из основных параметров слоя F2 — критической частоты foF2. Выявлена высокая корреляция между критической частотой слоя F2 и индексом солнечной активности F10.7. Показано, что в шести циклах солнечной активности (19–24 циклы) наблюдаются отрицательные тренды среднегодовых значений критических частот слоя F2 как в полуденные, так и в полуночные часы. Обнаружено, что тренды foF2 зависят от сезона и времени суток. Абсолютные значения трендов выше в равноденственные и летние сезоны. В полуденные часы в равноденственные месяцы наблюдаются пики отрицательных трендов, достигающие ~–11 кГц/год.

A statistical analysis of vertical ionospheric sounding data from the Yakutsk station (62.01° N, 129.43° E, 57.12° MLAT) for the period from 1956 to 2017 encompassing six solar cycles has been carried out to identify long-term changes in the F2 layer of the subauroral ionosphere and their relationship with solar and geomagnetic activity. We examined variations in one of the main parameters of the ionospheric F2 layer, the critical frequency. A high correlation was found between the F2-layer critical frequency and the solar activity index F10.7. It is shown that during six solar cycles (cycles 19–24) there were negative trends in annual average F2-layer critical frequencies both at midday and at midnight. It has been revealed that foF2 trends depend on the season and time of day. Absolute values of the trends are higher in equinoctial and summer seasons. Peak negative trends are observed at midday during equinoctial months, reaching approximately –11 kHz/year.

 долговременные тренды солнечная активность субавроральная ионосфера критическая частота слоя F2 long-term trends solar activity subauroral ionosphere F2-layer critical frequencies Исследование выполнено за счет гранта Российского научного фонда (проект № 25-17-20002) The work was financially supported by the Russian Science Foundation (Project No. 25-17-20002)

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