Complexity Variations in the Interplanetary Magnetic Field between 0.4 and 5.3 AU
Abstract
We have investigated how the character of magnetic fluctuations in solar wind depends on radial distance from the Sun. We use measurements of the magnetic field taken at different distances from the Sun by different spacecraft: Helios between 0.4 and 1 AU, Wind at about 1 AU, and Ulysses at about 5.4 AU. Data intervals are selected to contain turbulent magnetic fluctuations, coronal mass ejections (CMEs), and co-rotating interaction regions (CIRs). With these data we calculate the Jensen-Shannon complexity as a function of permutation entropy. Jensen-Shannon complexity maps indicate if the fluctuations in the magnetic fields are stochastic (low complexity) chaotic (maximal complexity and lower entropy), or chaotic with a strong noise component (moderate complexity and high entropy). The Jensen-Shannon complexity values determined from the spacecraft measurements for the turbulent magnetic fluctuations indicate the fluctuations are stochastic in nature. This observation is supported by power spectra. The Jensen-Shannon complexity values determined for the CMEs and CIRs indicate the fluctuations are chaotic. The CME Jensen-Shannon complexity values evolve from high complexity and moderate entropy at 1 AU to lower complexity and higher entropy farther from the Sun at 5.4 AU. We interpret these data to mean that as the solar wind plasma expands outward, the magnetic field fluctuations evolve from chaotic (i.e., low dimensionality, deterministic fluctuations) to stocastic (i.e., low dimensionality, non-deterministic fluctuations). These results can be tested by Solar Probe Plus to be launched in 2018.
- Publication:
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Solar Heliospheric and INterplanetary Environment (SHINE 2016)
- Pub Date:
- July 2016
- Bibcode:
- 2016shin.confE.181W