Geophysical research: article

A.V. Guglielmi 1 B.I. Klain 2 A.S. Potapov 3
1 Schmidt Institute of Physics of the Earth, Russian Academy of Sciences 2 Borok Geophysical Observatory, the Branch of Schmidt Institute of Physics of the Earth RAS 3 Institute of Solar-Terrestrial Physics SB RAS
Journal: Geophysical research
Tome: 24
Number: 1
Year: 2023
Pages: 74-84
UDK: 550.386
DOI: 10.21455/gr2023.1-5
Full text
Keywords: geoelectromagnetism, magnetohydrodynamics, magnetosphere, Alfvén wave, resonator, Sturm–Liouville prob-lem, Wentzel–Kramers–Brillouin (WKB) method.
Аnnotation: The idea of Alfvén waves plays a key role in the theory of ultra-low-frequency (ULF) electromagnetic oscilla-tions of cosmic origin. The article is dedicated to the 80th anniversary of the discovery of Alfvén waves. It focuses on the Ionospheric Alfvén Resonator, or IAR for short. ULF oscillations are excited in the IAR in the Pc1 range (0.2–5 Hz). When calculating the oscillation spectrum within the framework of the standard model, it is assumed that the IAR is an autonomous dynamic system. In contrast, in the presented article, the IAR is considered as a specific subsystem of the general system of Alfvén oscillations of geomagnetic field lines. In other words, authors proceed from the idea that the IAR, generally speaking, is not an autonomous oscillatory system. The problem of the IAR spectrum is discussed in this article within the framework of the general problem of the spectrum of MHD oscillations of the Earth's magnetosphere. The corresponding Sturm–Liouville problem is formulated. Analytical solutions of the problem are considered in the Wentzel–Kramers–Brillouin ap-proximation. The need for a numerical solution of the problem of the IAR spectrum is indicated in view of the rather complex distribution of the Alfvén velocity along geomagnetic field lines.
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