7 research outputs found
Hysteresis in a Solar Activity Cycle
We analyze in situ measurements of solar wind velocity obtained by the
Advanced Composition Explorer (ACE) spacecraft during the solar activity cycle
23. We calculated a robust complexity measure, the permutation entropy (S) of
solar wind time series at different phases of a solar activity cycle. The
permutation entropy measure is first tested on the known dynamical data before
its application to solar wind time series. It is observed that complexity of
solar wind velocity fluctuations at 1 AU shows hysteresis phenomenon while
following the ascending and descending phases of the activity cycle. This
indicates the presence of multistability in the dynamics governing the solar
wind velocity over a solar activity cycle.Comment: 10 pages, 5 figures; Solar Physics, 201
Symbolic analysis of slow solar wind data using rank order statistics
We analyze time series data of the fluctuations of slow solar wind velocity
using rank order statistics. We selected a total of 18 datasets measured by the
Helios spacecraft at a distance of 0.32 AU from the sun in the inner
heliosphere. The datasets correspond to the years 1975-1982 and cover the end
of the solar activity cycle 20 to the middle of the activity cycle 21. We first
apply rank order statistics to time series from known nonlinear systems and
then extend the analysis to the solar wind data. We find that the underlying
dynamics governing the solar wind velocity remains almost unchanged during an
activity cycle. However, during a solar activity cycle the fluctuations in the
slow solar wind time series increase just before the maximum of the activity
cycleComment: 10 pages, 7 figures, 1 tabl
Nonlinear Time Series Analysis of Sunspot Data
This paper deals with the analysis of sunspot number time series using the
Hurst exponent. We use the rescaled range (R/S) analysis to estimate the Hurst
exponent for 259-year and 11360-year sunspot data. The results show a varying
degree of persistence over shorter and longer time scales corresponding to
distinct values of the Hurst exponent. We explain the presence of these
multiple Hurst exponents by their resemblance to the deterministic chaotic
attractors having multiple centers of rotation.Comment: 10 pages, 6 figures, accepted for publication in Solar Physics,
journal style corrections done in this versio