@article{SchwarzBenzKurthsetal.1993,
  author    = {Schwarz, udo and Benz, Arnold O. and Kurths, J{\"u}rgen and Witt, Annette},
  title     = {Analysis of solar spike events by means of symbolic dynamics methods},
  issn      = {004-6361},
  year      = {1993},
  abstract  = {Using quantities of symbolic dynamics, such as mutual information, Shannon information and algorithmic complexity, we have searched for interrelations of spikes emitted simultaneously at different frequencies during the impulsive phase of a flare event. As the spikes are related to the flare energy release and are interpreted as emissions originating at different sites having different magnetic field strengths, any relation in frequency is interpretated as a relation in space. This approach is appropriate to characterize such spatio-temporal patterns, whereas the popular estimate of fractal dimensions can be applied to low-dimensional systems only. Depending on the energy release and emission processes, two types of fragmentation are possible: a scenario of global organization (spikes are emitted in a succession of similar events by the same system) or a scenario of local organization (many systems triggered by an initial event). Mutual information which is a generalization of correlation indicates a relation in frequency beyond the bandwidth of individual spikes. The scans in the spectrograms with large mutual information also show a low level of Shannon information and algorithmic complexity, indicating that the simultaneous appearance of spikes at other frequencies is not a completely stochastic phenomenon (white noise). It may be caused by a nonlinear deterministic system or by a Markov process. By means of mutual information we find a memory over frequency intervals up to 60 MHz. Shannon information and algorithmic complexity concern the mbox{whole} frequency region, i.e. the global source region. A global organization is also apparent in quasi-periodic changes of the Shannon information and algorithmic complexity in the range of 2 - 8 seconds. The finding is compatible with a scenario of local organization in which the information of one event spreads spatially and triggers further events at different places. The region is not an ensemble of independently flashing sources, each representing a system that cascades in energy after an initial trigger. On the contrary, there is a causal connection between the sources at any time. The analysis of the four spike events suggests that the structure in frequency is not stochastic but a process in which spikes at nearby locations are simultaneously triggered by a common exciter.},
  language  = {en}
}
@article{LaiGrebogiFeudeletal.1998,
  author    = {Lai, Ying Cheng and Grebogi, Celso and Feudel, Ulrike and Witt, Annette},
  title     = {Basin bifurcation in quasiperiodically forced systems},
  year      = {1998},
  language  = {en}
}
@article{WittFeudelPikovskij1997,
  author    = {Witt, Annette and Feudel, Ulrike and Pikovskij, Arkadij},
  title     = {Birth of strange nonchaotic attractors due to interior crisis},
  year      = {1997},
  language  = {en}
}
@unpublished{WittNeimanKurths1997,
  author    = {Witt, Annette and Neiman, Alexander and Kurths, J{\"u}rgen},
  title     = {Characterizing the dynamics of stochastic bistable systems by measures of complexity},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14556},
  year      = {1997},
  abstract  = {The dynamics of noisy bistable systems is analyzed by means of Lyapunov exponents and measures of complexity. We consider both the classical Kramers problem with additive white noise and the case when the barrier fluctuates due to additional external colored noise. In case of additive noise we calculate the Lyapunov exponents and all measures of complexity analytically as functions of the noise intensity resp. the mean escape time. For the problem of fluctuating barrier the usual description of the dynamics with the mean escape time is not sufficient. The application of the concept of measures of complexity allows to describe the structures of motion in more detail. Most complexity measures sign the value of correlation time at which the phenomenon of resonant activation occurs with an extremum.},
  language  = {en}
}
@book{WittNeimanKurths1997,
  author    = {Witt, Annette and Neiman, Alexander and Kurths, J{\"u}rgen},
  title     = {Characterizing the dynamics of stochastic bistable systems by measures of complexity},
  series = {Preprint NLD},
  volume    = {36},
  journal   = {Preprint NLD},
  publisher = {Univ. Potsdam},
  address   = {Potsdam},
  issn      = {1432-2935},
  pages     = {20 S. : graph. Darst.},
  year      = {1997},
  language  = {en}
}
@article{WittNeimanKurths1997,
  author    = {Witt, Annette and Neiman, Alexander and Kurths, J{\"u}rgen},
  title     = {Charakterizing the dynamics of stochastic bistable systems by measures of complexity},
  year      = {1997},
  language  = {en}
}
@article{FeudelGellertRuedigeretal.2003,
  author    = {Feudel, Fred and Gellert, Marcus and R{\"u}diger, Sten and Witt, Annette and Seehafer, Norbert},
  title     = {Dynamo effect in a driven helical flow},
  year      = {2003},
  language  = {en}
}
@article{PolitiWitt1999,
  author    = {Politi, Antonio and Witt, Annette},
  title     = {Fractal dimension of space-time chaos},
  year      = {1999},
  language  = {en}
}
@article{WittSchumann2005,
  author    = {Witt, Annette and Schumann, A. Y.},
  title     = {Holocene climate variability on millennial scales recorded in Greenland ice cores},
  issn      = {1023-5809},
  year      = {2005},
  language  = {en}
}
@article{WittSchumann2005,
  author    = {Witt, Annette and Schumann, A. Y.},
  title     = {Holocene climate variability on millennial scales recorded in Greenland ice cores},
  issn      = {1023-5809},
  year      = {2005},
  abstract  = {Climate variability is triggered by several solar and orbital cycles as well as by the intern ocean dynamics. Consequently, paleoclimate proxy records are expected to vary on very different time scales ranging from subdecadal to millennial duration. We demonstrate, that Foster's (Foster, 1996) wavelet analysis technique is an appropriate tool for investigating temporarily changing spectral properties of records characterized by awkward sampling quality, which is a typical feature of climate proxy records. By applying it to the Holocene part of different glaciochemical records of Greenland ice cores we proof evidence for a significant contribution of the 1.47 kiloyears cycle over alomst the entire Holocene},
  language  = {en}
}