Retrospective investigation of geomagnetic field time-series during the 2009 L'Aquila seismic sequence

2012 ◽  
Vol 530-531 ◽  
pp. 310-317 ◽  
Author(s):  
Fabrizio Masci ◽  
Manuele Di Persio
Keyword(s):  
Time Series ◽  
Geomagnetic Field ◽  
Seismic Sequence ◽  
Retrospective Investigation

scholarly journals Geomagnetic Virtual Observatories: monitoring geomagnetic secular variation with the Swarm satellites

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Magnus D. Hammer ◽  
Grace A. Cox ◽  
William J. Brown ◽  
Ciarán D. Beggan ◽  
Christopher C. Finlay
Keyword(s):  
Time Series ◽  
Secular Variation ◽  
Geomagnetic Field ◽  
Time Windows ◽  
Low Earth Orbit ◽  
Data Selection ◽  
Spherical Harmonic Analysis ◽  
Core Field ◽  
The Core ◽  
Swarm Satellites

AbstractWe present geomagnetic main field and secular variation time series, at 300 equal-area distributed locations and at 490 km altitude, derived from magnetic field measurements collected by the three Swarm satellites. These Geomagnetic Virtual Observatory (GVO) series provide a convenient means to globally monitor and analyze long-term variations of the geomagnetic field from low-Earth orbit. The series are obtained by robust fits of local Cartesian potential field models to along-track and East–West sums and differences of Swarm satellite data collected within a radius of 700 km of the GVO locations during either 1-monthly or 4-monthly time windows. We describe two GVO data products: (1) ‘Observed Field’ GVO time series, where all observed sources contribute to the estimated values, without any data selection or correction, and (2) ‘Core Field’ GVO time series, where additional data selection is carried out, then de-noising schemes and epoch-by-epoch spherical harmonic analysis are applied to reduce contamination by magnetospheric and ionospheric signals. Secular variation series are provided as annual differences of the Core Field GVOs. We present examples of the resulting Swarm GVO series, assessing their quality through comparisons with ground observatories and geomagnetic field models. In benchmark comparisons with six high-quality mid-to-low latitude ground observatories we find the secular variation of the Core Field GVO field intensities, calculated using annual differences, agrees to an rms of 1.8 nT/yr and 1.2 nT/yr for the 1-monthly and 4-monthly versions, respectively. Regular sampling in space and time, and the availability of data error estimates, makes the GVO series well suited for users wishing to perform data assimilation studies of core dynamics, or to study long-period magnetospheric and ionospheric signals and their induced counterparts. The Swarm GVO time series will be regularly updated, approximately every four months, allowing ready access to the latest secular variation data from the Swarm satellites.

scholarly journals Development and application of problem-oriented digital twins for magnetic observatories and variation stations

2021 ◽  
pp. 60-71
Author(s):  
Andrei Vorobev ◽  
Vyacheslav Pilipenko ◽  
Gulnara Vorobeva ◽  
Olga Khristodulo
Keyword(s):  
Time Series ◽  
Geomagnetic Field ◽  
Missing Values ◽  
Information Environment ◽  
Small Scale ◽  
Geomagnetic Variation ◽  
Digital Twin ◽  
Digital Twins ◽  
Geomagnetic Data ◽  
Magnetic Station

Introduction: Magnetic stations are one of the main tools for observing the geomagnetic field. However, gaps and anomalies in time series of geomagnetic data, which often exceed 30% of the number of recorded values, negatively affect the effectiveness of the implemented approach and complicate the application of mathematical tools which require that the information signal is continuous. Besides, the missing values ​​add extra uncertainty in computer simulation of dynamic spatial distribution of geomagnetic variations and related parameters. Purpose: To develop a methodology for improving the efficiency of technical means for observing the geomagnetic field. Method: Creation of problem-oriented digital twins of magnetic stations, and their integration into the collection and preprocessing of geomagnetic data, in order to simulate the functioning of their physical prototypes with a certain accuracy. Results: Using Kilpisjärvi magnetic station (Finland) as an example, it is shown that the use of digital twins, whose information environment is made up of geomagnetic data from adjacent stations, can provide the opportunity for reconstruction (retrospective forecast) of geomagnetic variation parameters with a mean square error in the auroral zone of up to 11.5 nT. The integration of problem-oriented digital twins of magnetic stations into the processes of collecting and registering geomagnetic data can provide automatic identification and replacement of missing and abnormal values, increasing, due to the redundancy effect, the fault tolerance of the magnetic station as a data source object. For example, the digital twin of Kilpisjärvi station recovers 99.55% of annual information, and 86.73% of it has an error not exceeding 12 nT. Discussion: Due to the spatial anisotropy of geomagnetic field parameters, the error at the digital twin output will be different in each specific case, depending on the geographic location of the magnetic station, as well as on the number of the surrounding magnetic stations and the distance to them. However, this problem can be minimized by integrating geomagnetic data from satellites into the information environment of the digital twin. Practical relevance: The proposed methodology provides the opportunity for automated diagnostics of time series of geomagnetic data for outliers and anomalies, as well as restoration of missing values and identification of small-scale disturbances.

scholarly journals Observation of Intermittency-Induced Critical Dynamics in Geomagnetic Field Time Series Prior to the Intense Magnetic Storms of March, June, and December 2015

2018 ◽  
Vol 123 (6) ◽  
pp. 4594-4613 ◽  
Author(s):  
Georgios Balasis ◽  
Ioannis A. Daglis ◽  
Yiannis Contoyiannis ◽  
Stelios M. Potirakis ◽  
Constantinos Papadimitriou ◽  
...  
Keyword(s):  
Time Series ◽  
Geomagnetic Field ◽  
Magnetic Storms ◽  
Critical Dynamics

scholarly journals Statistical issues about solar–climate relations

2010 ◽  
Vol 6 (5) ◽  
pp. 565-573 ◽  
Author(s):  
P. Yiou ◽  
E. Bard ◽  
P. Dandin ◽  
B. Legras ◽  
P. Naveau ◽  
...  
Keyword(s):  
Time Series ◽  
Solar Activity ◽  
Geomagnetic Field ◽  
Degrees Of Freedom ◽  
Statistical Significance ◽  
Data Sets ◽  
Statistical Issues ◽  
The Relationship ◽  
Temperature Time ◽  
Field Variability

Abstract. The relationship between solar activity and temperature variation is a frequently discussed issue in climatology. This relationships is usually hypothesized on the basis of statistical analyses of temperature time series and time series related to solar activity. Recent studies (Le Mouël et al., 2008, 2009; Courtillot et al., 2010) focus on the variabilities of temperature and solar activity records to identify their relationships. We discuss the meaning of such analyses and propose a general framework to test the statistical significance for these variability-based analyses. This approach is illustrated using European temperature data sets and geomagnetic field variations. We show that tests for significant correlation between observed temperature variability and geomagnetic field variability is hindered by a low number of degrees of freedom introduced by excessively smoothing the variability-based statistics.

scholarly journals Geomagnetic jerks characterization via spectral analysis

Solid Earth ◽  
2012 ◽  
Vol 3 (1) ◽  
pp. 131-148 ◽  
Author(s):  
B. Duka ◽  
A. De Santis ◽  
M. Mandea ◽  
A. Isac ◽  
E. Qamili
Keyword(s):  
Time Series ◽  
Geomagnetic Field ◽  
Synthetic Data ◽  
Spatial Evolution ◽  
Spectral Techniques ◽  
The Third ◽  
Rapid Changes ◽  
Geomagnetic Jerks ◽  
Third Derivative ◽  
Harmonic Power

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.

scholarly journals Using spectral analysis to detect singular events such as jerks in the geomagnetic field time series

2011 ◽  
Vol 3 (2) ◽  
pp. 615-654
Author(s):  
B. Duka ◽  
A. De Santis ◽  
M. Mandea ◽  
A. Isac ◽  
E. Qamili
Keyword(s):  
Time Series ◽  
Spectral Analysis ◽  
Geomagnetic Field ◽  
Synthetic Data ◽  
Global Scale ◽  
Spherical Harmonic Analysis ◽  
Global Models ◽  
Spectral Techniques ◽  
Rapid Changes ◽  
Geomagnetic Jerks

Abstract. In this study we have applied two spectral techniques in terms of Fourier and wavelet analysis to geomagnetic field time series and compared the results with those obtained from analogous analyses to synthetic data. Then, an algorithm has been proposed to detect the geomagnetic jerks in time series, mainly being considered by the Eastern component secular variation. 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 on global scale, since the beginning of XXth century. Finally, a spherical harmonic analysis of the secular acceleration power spectrum has been computed since 1960 to 2000, bringing new insights in understanding these rapid changes of the geomagnetic field and their origin.

scholarly journals Repeat-station surveys: implications from chaos and ergodicity of the recent geomagnetic field

2013 ◽  
Vol 56 (1) ◽  
Author(s):  
Angelo De Santis ◽  
Enkelejda Qamili ◽  
Gianfranco Cianchini
Keyword(s):  
Time Series ◽  
Phase Space ◽  
Time Domain ◽  
Secular Variation ◽  
Geomagnetic Field ◽  
Repeat Station ◽  
Reconstructed Phase Space ◽  
Time Averages ◽  
The Time Domain ◽  
Strong Necessity

<p>The present geomagnetic field is chaotic and ergodic: chaotic because it can no longer be predicted beyond around 6 years; and ergodic in the sense that time averages correspond to phase-space averages. These properties have already been deduced from complex analyses of observatory time series in a reconstructed phase space and from global predicted and definitive models of differences in the time domain. These results imply that there is a strong necessity to make repeat-station magnetic surveys more frequently than every 5 years. This, in turn, will also improve the geomagnetic field secular variation models. This report provides practical examples and case studies.</p><p> </p>

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