Abstract
Abstract. In this study we have applied spectral techniques to analyze geomagnetic field time-series provided by observatories, and compared the results with those obtained from analogous analyses of synthetic data estimated from models. Then, an algorithm is here proposed to detect the geomagnetic jerks in time-series, mainly occurring in the eastern component of the geomagnetic field. Applying such analysis to time-series generated from global models has allowed us to depict the most important space-time features of the geomagnetic jerks all over the globe, since the beginning of XXth century. Finally, the spherical harmonic power spectrum of the third derivative of the main geomagnetic field has been computed from 1960 to 2002.5, bringing new insights to understand the spatial evolution of these rapid changes of the geomagnetic field.
Highlights
Studies of discrete time-series of physical quantities are widely interesting for their forecasting, and for defining both nature and behavior of the underlying physical phenomena
At higher latitude observatories the geomagnetic jerks noted in the original signals are difficult to be detected in the respective spectrograms
In order to detect any relation between the known jerk events and the time changes of the spherical harmonic of different degrees, we have investigated the time variations of the Mauersberger-Lowes power spectrum terms of different degrees (Lowes, 1974, 2007) extending its definition to the third derivative of Gauss coefficients: Rn3d =
Summary
Studies of discrete time-series of physical quantities are widely interesting for their forecasting, and for defining both nature and behavior of the underlying physical phenomena. Different methods of time-series analyses have been used to study the geomagnetic field which is, at all times, subject to temporal variations on a wide range of time scales. When the wavelet technique has been applied to series of monthly means, it appears that the event reveals a singular behavior with a fractional derivative close to an order 1.5. This interesting behavior would be useful to analyze the geomagnetic jerks at the place of their origin, the top of the core. We have used three different methods to study time-series of geomagnetic field components and secular variations, with particular attention to the Y component.
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