Trigger excitation of "pearls" in the Earth's magnetosphere: On the 90th anniversary of the discovery of Pc1 waves

Abstract

Ultra-low-frequency electromagnetic waves Pc1 (0.2-5 Hz), widely known in the literature as pearls, are excited in the outer radiation belt and propagate to the Earth along the geomagnetic field lines in the form of Alfven waves. The study of pearls is of considerable interest for magnetospheric physics. Both spontaneous and stimulated pearl excitation are observed. The paper examines stimulated (trigger) excitation of pearls. A classification of triggers acting on dynamic systems of the magnetosphere is presented. 2 types, 4 classes and 8 species of triggers have been introduced. Examples of triggers of natural and artificial origin are given. The concept of a trigger cascade is introduced. Particular attention is paid to the anthropogenic periodic trigger of pearls. It manifests itself in the form of the so-called Big Ben effect. The essence of the effect is that a series of pearls is often excited immediately following the hour marker according to world time. It is claimed that the connection between the excitation of pearls and hour markers is not accidental, but represents a rather mysterious geophysical phenomenon. It is assumed that the Big Ben effect occurs as a result of the impact on the radiation belt of an unknown type of endogenous periodic artificial trigger. Key words: oscillations and waves, Alfven waves, ion-cyclotron resonator, radiation belt, instability, classification, natural and artificial, technosphere, Big Ben effect.