Solar-Terrestrial Physics Solar-Terrestrial Physics Solar-Terrestrial Physics 2500-0535 16403 10.12737/article_58f97156b06fa5.51468016 Results of current research Results of current research Results of current research Resonant ULF absorption in storm time conditions Resonant ULF absorption in storm time conditions Бадин Владимир Иванович Badin Vladimir Ivanovich badin@izmiran.ru

кандидат физико-математических наук;

candidate of physical and mathematical sciences;

 Институт земного магнетизма, ионосферы и распространения радиоволн им. Н.В. Пушкова РАН Москва Россия Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation RAS Moscow Russian Federation 3 1 103 113 https://zh-szf.ru/en/nauka/article/16403/view

The work deals with ULF radar observations of the high-latitude ionosphere. Doppler data from the Norwegian STARE instrument are analyzed for the moderate magnetic storm observed on December 31, 1999–January 01, 2000. Upon averaging the Doppler signals along radar beams, the spectral power of signals is determined for each beam as a function of frequency ranging from 1 to 10 mHz. Sharp drops (about 10 dB) of spectral powers with frequency are found for all radar beams. A variational analysis of spectral powers is carried out by least squares, with power drops being modeled by stepwise profiles constructed of mean spectral powers preceding and succeeding the drops. Using this variational analysis, the frequency of the power drop is determined for each radar beam. Being averaged over all beams, this frequency is 4.8 ± 0.5 mHz. The results obtained are interpreted as resonant absorption of ultra-low-frequency (ULF) waves occurring on eigenfrequencies of magnetic field lines over wave propagation from the magnetopause deep into the magnetosphere.

The work deals with ULF radar observations of the high-latitude ionosphere. Doppler data from the Norwegian STARE instrument are analyzed for the moderate magnetic storm observed on December 31, 1999–January 01, 2000. Upon averaging the Doppler signals along radar beams, the spectral power of signals is determined for each beam as a function of frequency ranging from 1 to 10 mHz. Sharp drops (about 10 dB) of spectral powers with frequency are found for all radar beams. A variational analysis of spectral powers is carried out by least squares, with power drops being modeled by stepwise profiles constructed of mean spectral powers preceding and succeeding the drops. Using this variational analysis, the frequency of the power drop is determined for each radar beam. Being averaged over all beams, this frequency is 4.8 ± 0.5 mHz. The results obtained are interpreted as resonant absorption of ultra-low-frequency (ULF) waves occurring on eigenfrequencies of magnetic field lines over wave propagation from the magnetopause deep into the magnetosphere.

 ULF waves electric fields high-latitude ionosphere

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