Аннотация
A multifractal formalism is employed to analyse high-precision
time-series data of Kepler stars with surface differential rotation (DR)
traces. The multifractal detrended moving average (MFDMA) algorithm has
been explored to characterize the multiscale behaviour of the observed
time series from a sample of 662 stars selected with parameters close to
those of the Sun (e.g. effective temperature, mass, effective gravity
and rotation period). Among these stars, 141 have surface DR traces,
whereas 521 have no detected DR signatures. In our sample, we also
include the Sun in its active phase. Our results can be summarized in
two points. First, our work suggests that star-spots for time series
with and without DR have distinct dynamics. Secondly, the magnetic
fields of active stars are apparently governed by two mechanisms with
different levels of complexity for fluctuations. Throughout the course
of the study, we identified an overall trend whereby the DR is
distributed in two H regimes segregated by the degree of asymmetry A,
where H-index denotes the global Hurst exponent that is used as a
measure of long-term memory of time series. As a result, we show that
the degree of asymmetry can be considered a segregation factor that
distinguishes the DR behaviour when related to the effect of the
rotational modulation on the time series. In summary, the
multifractality signals in our sample are the result of magnetic
activity control mechanisms leading to activity-related long-term
persistent signatures.
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