Maximum Likelihood Parameter Estimation and Simulation of Damped-Type ULF Waves Using a Workstation

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Various computer programs for data processing have been developed on a workstation, and parameter estimations and simulations of damped-type ULF waves have been per-formed using the workstation. Research results are as follows : 1.While a method for fitting a piecewise cubic polynomial (PCP) to a sequence of data, which corresponds to a nonlinear lowpass filter and is named a PCP filter, is accompanied with a parameter mu determing the degree of smoothing, the relation between mu and its cutoff frequency has been found.The PCP filter is effective in separating Psc's from main impulses of SSC's. 2. Although a modified Pisarenko method (MPM) is inferior in estimation ability to the maximum likelihood method (MLM), it is one of the methods with the highest perfor-mance except for the MLM and is much superior in computational cost to the MLM.It has been used in the analysis of the Psc's. 3. The shape of the waveform of low-latitude and equatorial Psc's is consistently ordered by local time ; it is steeper near noon and has a more moderate slope near midnight. They have globally almost identical dominant frequencies which agree well with those of Pi2's. These indicate that the Psc's are not cavity-mode oscillations but compressional hydromagnetic (HM) waves propagating from dayside to nightside. 4. The self-consistent ionospheric boundary conditions, which de-scribe the interaction between HM waves and the anisotropically conducting ionosphere, have been derived in the form convenient for the eigenmode analysis of coupled HM waves in the magnetosphere-ionosphere system.