CONSIDERATIONS ON GEOMAGNETIC DATA ANALYSIS
地磁数据分析的一些思考

This article aims to make a few remarks, examples and results about methods for analysis of geomagnetic data. In our study we used several methods and algorithms about numerical derivatives depending on time, polynomial regression, correlation factor, spectral analysis and wavelet analysis. With these algorithms were developed several programs in MatLab and AutoSignal software to study geomagnetic field morphology and to determine the spectrum of geomagnetic phenomena in different time intervals. Considering some period of time geomagnetic data recorded at the Observatory Surlari (colatitude 45.3°, longitude 26.3°) and comparing them with data recorded at other observatories, such as Ottawa (colatitude 44.6°, longitude 284.5°), Canberra (colatitude 125.3°, longitude 149.3°), Kakioka (colatitude 53.8°, longitude 140.2°) and Vernadsky (colatitude 155.3°, longitude 295.7°), including comparison to the windowed Fourier transform, the choice of an appropriate wavelet basis function, edge effects due to finite-length time series, and the relationship between wavelet scale and Fourier frequency. From geomagnetic data analysis (spectral and wavelet) on definitive data in year 2007 recorded at two observatories to show that disadvantages of applying only the spectral analysis are related to less capacity of locating frequencies, amplitudes and phases in time. Also, the advantages and disadvantages of Fourier Transform and Wavelet Transform are discussed.