Spectral power of low-latitude Pi 2 pulsations at the 210° magnetic meridian stations and plasmaspheric cavity resonances
© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2000
Received: 15 March 2000
Accepted: 17 August 2000
Published: 20 June 2014
Pi 2 pulsations at low latitudes are examined with magnetic fields data at the 210° magnetic meridian (MM) stations in 1991. Due to high degree of coherence over most latitudes, 68 low-latitude Pi 2 events at the 210° MM stations are identified with reference to same waveforms on the magnetogram at Lunping (189.5° MM, L = 1.06). With spectral power analysis, the ratio of the first four harmonic frequencies of low-latitude Pi 2 pulsations is about 1: (1.7 ± 0.1): (2.3 ± 0.1): (2.9 ± 0.1). By using abox model for the inner magnetosphere, the cold linearized MHD wave equations are studied with realistic Alfven speed profile for nonuniform ambient magnetic fields. With appropriate parameters to depict the magnetospheric environments during the aforementioned period, numerical results are acquired with the fourth order Runge-Kutta method. It is found that the ratio of the first four harmonic frequencies of plasmaspheric cavity resonances is about 1: 1.7: 2.4: 3.1 that is consistent with data analysis. This suggests that low-latitude Pi 2 pulsations at the 210° MM stations may be plasmaspheric cavity resonances driven by fast compressional waves owing to the impulsive source at the magnetotail.