  We present a dimension analysis of a set of solar type I storms and type IV
events with different kind of fine structures, recorded at the Trieste
Astronomical Observatory. The signature of such types of solar radio events is
highly structured in time. However, periodicities are rather seldom, and linear
mode theory can provide only limited interpretation of the data. Therefore, we
performed an analysis based on methods of the nonlinear dynamics theory.
Additionally to the commonly used correlation dimension, we also calculated
local pointwise dimensions. This alternative approach is motivated by the fact
that astrophysical time series represent real-world systems, which cannot be
kept in a controlled state and which are highly interconnected with their
surroundings. In such systems pure determinism is rather unlikely to be
realized, and therefore a characterization by invariants of the dynamics might
probably be inadequate. In fact, the outcome of the dimension analysis does not
give hints for low-dimensional determinism in the data, but we show that,
contrary to the correlation dimension method, local dimension estimations can
give physical insight into the events even in cases in which pure determinism
cannot be established. In particular, in most of the analyzed radio events
nonlinearity in the data is detected, and the local dimension analysis provides
a basis for a quantitative description of the time series, which can be used to
characterize the complexity of the related physical system in a comparative and
non-invariant manner.
