Publication: Random Walk and Trapping of Interplanetary Magnetic Field Lines: Global Simulation, Magnetic Connectivity, and Implications for Solar Energetic Particles
Issued Date
2021-02-20
Resource Type
ISSN
15384357
0004637X
0004637X
Other identifier(s)
2-s2.0-85102708710
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Mahidol University
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SCOPUS
Bibliographic Citation
Astrophysical Journal. Vol.908, No.2 (2021)
Suggested Citation
Rohit Chhiber, David Ruffolo, William H. Matthaeus, Arcadi V. Usmanov, Paisan Tooprakai, Piyanate Chuychai, Melvyn L. Goldstein Random Walk and Trapping of Interplanetary Magnetic Field Lines: Global Simulation, Magnetic Connectivity, and Implications for Solar Energetic Particles. Astrophysical Journal. Vol.908, No.2 (2021). doi:10.3847/1538-4357/abd7f0 Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/76864
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Title
Random Walk and Trapping of Interplanetary Magnetic Field Lines: Global Simulation, Magnetic Connectivity, and Implications for Solar Energetic Particles
Abstract
The random walk of magnetic field lines is an important ingredient in understanding how the connectivity of the magnetic field affects the spatial transport and diffusion of charged particles. As solar energetic particles propagate away from near-solar sources, they interact with the fluctuating magnetic field, which modifies their distributions. We develop a formalism in which the differential equation describing the field line random walk contains both effects due to localized magnetic displacements and a non-stochastic contribution from the large-scale expansion. We use this formalism together with a global magnetohydrodynamic simulation of the inner-heliospheric solar wind, which includes a turbulence transport model, to estimate the diffusive spreading of magnetic field lines that originate in different regions of the solar atmosphere. We first use this model to quantify field line spreading at 1 au, starting from a localized solar source region, and find rms angular spreads of about 20 -60 . In the second instance, we use the model to estimate the size of the source regions from which field lines observed at 1 au may have originated, thus quantifying the uncertainty in calculations of magnetic connectivity; the angular uncertainty is estimated to be about 20 . Finally, we estimate the filamentation distance, i.e., the heliocentric distance up to which field lines originating in magnetic islands can remain strongly trapped in filamentary structures. We emphasize the key role of slab-like fluctuations in the transition from filamentary to more diffusive transport at greater heliocentric distances.