Complexity Variations in the Interplanetary Magnetic Field Between 0.3 and 5.4 AU
Abstract
We have investigated how the character of magnetic fluctuations in the 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 0.3 and 1 AU and Ulysses between 1.4 and 5.4 AU. We selected data intervals determined to have only turbulent magnetic field fluctuations and no other structures. 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 Helios and Ulysses spacecraft measurements for the turbulent magnetic fluctuations indicate the fluctuations are stochastic. This conclusion is supported by power spectra. The Jensen-Shannon complexity values calculated for slow (<450 km/s) and fast solar wind (>550 km/s) turbulent magnetic field fluctuations evolve from low complexity and high entropy at 1 AU to lower complexity and higher entropy farther from the Sun (to 5.4 AU). No clear dependence on heliospheric latitude is apparent in the Ulysses data. We interpret these data to mean that the magnetic field fluctuations become more stochastic at greater distances from the Sun. We investigate whether with this change in complexity is due to expansion of the solar wind or the age of the turbulent magnetic fluctuations. These results can be tested by Solar Probe Plus in 2018.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMSH41A2511W
- Keywords:
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- 2149 MHD waves and turbulence;
- INTERPLANETARY PHYSICSDE: 2164 Solar wind plasma;
- INTERPLANETARY PHYSICSDE: 7827 Kinetic and MHD theory;
- SPACE PLASMA PHYSICSDE: 7863 Turbulence;
- SPACE PLASMA PHYSICS