@article{AsariWardinski2018,
  author    = {Asari, Seiki and Wardinski, Ingo},
  title     = {Interannual fluctuations of the core angular momentum inferred from geomagnetic field models},
  series = {Magnetic Fields in the Solar System : Planets, Moons and Solar Wind Interactions},
  volume    = {448},
  journal   = {Magnetic Fields in the Solar System : Planets, Moons and Solar Wind Interactions},
  publisher = {Springer},
  address   = {Dordrecht},
  isbn      = {978-3-319-64292-5},
  issn      = {0067-0057},
  doi       = {10.1007/978-3-319-64292-5_4},
  pages     = {111 -- 123},
  year      = {2018},
  language  = {en}
}
@article{LesurWardinskiBaerenzungetal.2017,
  author    = {Lesur, Vincent and Wardinski, Ingo and B{\"a}renzung, Julien and Holschneider, Matthias},
  title     = {On the frequency spectra of the core magnetic field Gauss coefficients},
  series = {Physics of the earth and planetary interiors},
  volume    = {276},
  journal   = {Physics of the earth and planetary interiors},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0031-9201},
  doi       = {10.1016/j.pepi.2017.05.017},
  pages     = {145 -- 158},
  year      = {2017},
  abstract  = {From monthly mean observatory data spanning 1957-2014, geomagnetic field secular variation values were calculated by annual differences. Estimates of the spherical harmonic Gauss coefficients of the core field secular variation were then derived by applying a correlation based modelling. Finally, a Fourier transform was applied to the time series of the Gauss coefficients. This process led to reliable temporal spectra of the Gauss coefficients up to spherical harmonic degree 5 or 6, and down to periods as short as 1 or 2 years depending on the coefficient. We observed that a k(-2) slope, where k is the frequency, is an acceptable approximation for these spectra, with possibly an exception for the dipole field. The monthly estimates of the core field secular variation at the observatory sites also show that large and rapid variations of the latter happen. This is an indication that geomagnetic jerks are frequent phenomena and that significant secular variation signals at short time scales - i.e. less than 2 years, could still be extracted from data to reveal an unexplored part of the core dynamics.},
  language  = {en}
}
@article{AsariWardinski2015,
  author    = {Asari, Seiki and Wardinski, Ingo},
  title     = {On magnetic estimation of Earth's core angular momentum variation},
  series = {Journal of geophysical research : Solid earth},
  volume    = {120},
  journal   = {Journal of geophysical research : Solid earth},
  number    = {10},
  publisher = {American Geophysical Union},
  address   = {Washington},
  issn      = {2169-9313},
  doi       = {10.1002/2014JB011458},
  pages     = {6740 -- 6757},
  year      = {2015},
  abstract  = {We study systematically the estimation of Earth's core angular momentum (CAM) variation between 1962.0 and 2008.0 by using core surface flow models derived from the recent geomagnetic field model C(3)FM2. Various flow models are derived by changing four parameters that control the least squares flow inversion. The parameters include the spherical harmonic (SH) truncation degree of the flow models and two Lagrange multipliers that control the weights of two additional constraints. The first constraint forces the energy spectrum of the flow solution to follow a power law l-p, where l is the SH degree and p is the fourth parameter. The second allows to modulate the solution continuously between the dynamical states of tangential geostrophy (TG) and tangential magnetostrophy (TM). The calculated CAM variations are examined in reference to two features of the observed length-of-day (LOD) variation, namely, its secular trend and 6year oscillation. We find flow models in either TG or TM state for which the estimated CAM trends agree with the LOD trend. It is necessary for TM models to have their flows dominate at planetary scales, whereas TG models should not be of this scale; otherwise, their CAM trends are too steep. These two distinct types of flow model appear to correspond to the separate regimes of previous numerical dynamos that are thought to be applicable to the Earth's core. The phase of the subdecadal CAM variation is coherently determined from flow models obtained with extensively varying inversion settings. Multiple sources of model ambiguity need to be allowed for in discussing whether these phase estimates properly represent that of Earth's CAM as an origin of the observed 6year LOD oscillation.},
  language  = {en}
}
@article{KirvovWardinskiSpahnetal.2002,
  author    = {Kirvov, Alexander V. and Wardinski, Ingo and Spahn, Frank and Kr{\"u}ger, Harald and Gr{\"u}n, Eberhard},
  title     = {Dust on the outskirts of the Jovian System},
  year      = {2002},
  language  = {en}
}
@article{TimmerSchwarzVossetal.2000,
  author    = {Timmer, Jens and Schwarz, Udo and Voss, Henning U. and Wardinski, Ingo and Belloni, Tomaso and Hasinger, G{\"u}nther and VanDerKlis, Michael and Kurths, J{\"u}rgen},
  title     = {Linear and Nonlinear Time Series Analysis of the Black Hole Candidate Cygnus X-1},
  year      = {2000},
  abstract  = {We analyze the variability in the x-ray lightcurves of the black hole candidate Cygnus X-1 by linear and nonlinear time series analysis methods. While a linear model describes the overall second order properties of the observed data well, surrogate data analysis reveals a significant deviation from linearity. We discuss the relation between shot noise models usually applied to analyze these data and linear stochastic autoregressive models. We debate statistical and interpretational issues of surrogate data testing for the present context. Finally, we suggest a combination of tools from linear and nonlinear time series analysis methods as a procedure to test the predictions of astrophysical models on observed data.},
  language  = {en}
}