Solar-Terrestrial Physics Solar-Terrestrial Physics Solar-Terrestrial Physics 2500-0535 49989 10.12737/stp-84202205 Results of current research Results of current research Results of current research Peculiarities of ULF wave characteristics in a multicomponent ionospheric plasma Peculiarities of ULF wave characteristics in a multicomponent ionospheric plasma Котик Дмитрий Самойлович Kotik Dmitriy Samoylovich dmitry.kotik@nirfi.unn.ru

кандидат физико-математических наук;

candidate of physical and mathematical sciences;

 Орлова Екатерина Валерьевна Orlova Ekaterina Valeryevna ekaterina.orlova.94@bk.ru Яшнов Владимир Александрович Yashnov Vladimir Aleksandrovich

кандидат физико-математических наук;

candidate of physical and mathematical sciences;

 Научно-исследовательский радиофизический институт Нижний Новгород Россия Radiophysical Research Institute Nizhny Novgorod Russian Federation Нижегородский государственный университет им. Н.И. Лобачевского the Leading and National Research Nizhigorodsky State University named after N.I. Lobachevsky 24 12 2022 24 12 2022 8 4 55 62 07 04 2022 17 10 2022 https://zh-szf.ru/en/nauka/article/49989/view

We have examined the properties of low-frequency electromagnetic waves in multicomponent ionospheric plasma in the 1–30 Hz band, using the magnetoionic theory. Complex permittivity tensor components and refractive indices of normal waves (ordinary and extraordinary) were calculated at altitudes from 80 to 750 km. The calculations show that the refractive indices are highly dependent on frequency and height. Polarization of ordinary and extraordinary waves is elliptical over the entire range of the frequencies investigated. The refractive index and the polarization of normal waves are demonstrated to tend to magnetohydrodynamic (MHD) values only at frequencies lower than 1 Hz. The group velocity vector of an extraordinary wave is not directed along the magnetic field, as follows from the MHD approximation, but it lies inside a cone within ±(5–10) degrees, depending on frequency. The group velocity vector of an ordinary wave is practically independent of the angle with the geomagnetic field as in the MHD approximation. The proposed method for calculating the characteristics of normal waves in the ionosphere can be used to study ULF wave propagation from both natural and artificial ionospheric sources, which arise under the action of powerful HF radio waves in the lower and upper ionosphere.

We have examined the properties of low-frequency electromagnetic waves in multicomponent ionospheric plasma in the 1–30 Hz band, using the magnetoionic theory. Complex permittivity tensor components and refractive indices of normal waves (ordinary and extraordinary) were calculated at altitudes from 80 to 750 km. The calculations show that the refractive indices are highly dependent on frequency and height. Polarization of ordinary and extraordinary waves is elliptical over the entire range of the frequencies investigated. The refractive index and the polarization of normal waves are demonstrated to tend to magnetohydrodynamic (MHD) values only at frequencies lower than 1 Hz. The group velocity vector of an extraordinary wave is not directed along the magnetic field, as follows from the MHD approximation, but it lies inside a cone within ±(5–10) degrees, depending on frequency. The group velocity vector of an ordinary wave is practically independent of the angle with the geomagnetic field as in the MHD approximation. The proposed method for calculating the characteristics of normal waves in the ionosphere can be used to study ULF wave propagation from both natural and artificial ionospheric sources, which arise under the action of powerful HF radio waves in the lower and upper ionosphere.

 ULF waves ionosphere refractive index polarization Alfvén wave fast magnetosonic wave ULF waves ionosphere refractive index polarization Alfvén wave fast magnetosonic wave The work was financially supported by the Russian Science Foundation: development of the multicomponent ionospheric plasma model under Project No. 20-17-00050 and calculations of characteristics of normal ULF waves in the ionosphere under Project No. 20-12-00197 The work was financially supported by the Russian Science Foundation: development of the multicomponent ionospheric plasma model under Project No. 20-17-00050 and calculations of characteristics of normal ULF waves in the ionosphere under Project No. 20-12-00197

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