Harmonic structure of Pc 3-4 pulsations

摘要: Power spectra of magnetic pulsations observed at synchronous orbit by the ATS 6 satellite often show several spectral peaks simultaneously. Such pulsations, which we call harmonic events because nearly constant separation between successive peaks, are continuously in dayside Pc 3–4 frequency range (6.6–100 mHz). The seen clearly only east-west field component. regularly spaced with a typical minimum 14 mHz morning gradually decreasing to 10 afternoon. In dynamic events, fundamental mode is usually absent. addition, relative amplitudes higher harmonics depend on latitude. These features can be explained standing Alfven wave consisting many discrete frequencies. A statistical analysis power demonstrates that least 10–30% 3 classified as events. Using able estimate plasma mass density. For selected event August 7, 1975, density estimated 3–8 hydrogen mass/cm³.