Discrete Spectral Structure of Low-Latitude and Equatorial Pi2 Pulsation

A Pi2 event observed simultaneously at three low-latitude and equatorial stations is analyzed using a new maximum likelihood method, and found to be mathematically composed of multiple exponentially damped sinusoids, of which frequencies are almost identical at the three stations. This is a piece of evidence to support the existence of the global mode cavity resonance. A numerical eigen-mode analysis of the decoupled poloidal wave equation with the outer boundary of the cavity located at the plasmapause can not sufficiently explain the observed discrete frequencies of the Pi2 event, so that the global cavity with the outer boundary outside the plasmapause is inevitably invoked.

[1]  M. Itonaga,et al.  Maximum likelihood parameter estimation of suddenly-commencing equatorial Pi2 pulsations , 1991 .

[2]  Dong-Hun Lee,et al.  Impulsive excitation of ULF waves in the three‐dimensional dipole model: The initial results , 1991 .

[3]  K. Yumoto,et al.  On the cavity mode nature of low‐latitude Pi 2 pulsations , 1991 .

[4]  H. Lühr,et al.  Multiple ground-based and satellite observations of global Pi 2 magnetic pulsations , 1990 .

[5]  Dong-Hun Lee,et al.  Magnetospheric ULF wave coupling in the dipole model: The impulsive excitation , 1989 .

[6]  K. Yumoto,et al.  dayside Pi 2 pulsations at low latitudes , 1989 .

[7]  G. Crowley,et al.  Observational evidence of cavity modes in the Earth's magnetosphere , 1987 .

[8]  W. Allan,et al.  Hydromagnetic wave coupling in the magnetosphere—Plasmapause effects on impulse-excited resonances , 1986 .

[9]  E. M. Poulter,et al.  Impulse-excited hydromagnetic cavity and field-line resonances in the magnetosphere , 1986 .

[10]  M. Kivelson,et al.  Coupling of global magnetospheric MHD eigenmodes to field line resonances , 1986 .

[11]  W. Allan,et al.  Magnetospheric coupling of hydromagnetic waves ‐ Initial results , 1985 .

[12]  J. Samson,et al.  Latitude‐dependent characteristics of high‐latitude Pc 4 and Pc 5 micropulsations , 1972 .

[13]  H. Radoski,et al.  Axisymmetric Plasmasphere Resonances: Toroidal Mode , 1966 .

[14]  K. Yumoto.  Evidences of Magnetospheric Cavity Pi2 Waves , 1990 .

[15]  T. Araki,et al.  Global mode of Pi2 waves in the equatorial region ― Difference of Pi2 mode between high and equatorial latitudes , 1988 .

[16]  O. Saka,et al.  A Compact Magnetometer Data Acquisition System with Accurate Chronometer , 1986 .

[17]  David J. Southwood,et al.  Resonant ULF waves: A new interpretation , 1985 .