New insights from modeling the neutral heliospheric current sheet
Recently, the modulation of cosmic rays in the heliosphere has increasingly been studied by solving the well known transport equation via an approach based on stochastic differential equations. This approach, which is now well-established and published, allows for an in depth study of the modulation effects of the wavy heliospheric current sheet, in particular as its waviness increases with solar activity up to extreme maximum conditions. This is possible because of the numerical stability of the approach as well as its ability to trace pseudo-particles so that insightful trajectories of how they respond to the wavy heliospheric current sheet can be computed and displayed. Utilising such a stochastic model, we present valuable new insights into how the geometry of the wavy current sheet can affect the modulation of cosmic rays, especially at the highest levels of solar activity. This enables us to show, from a modeling perspective, why a certain choice for the current sheet profile is more suited than another at these high solar activity levels. We emphasise the importance of an effective tilt angle and illustrate how this concept can be employed effectively in interpreting results pertaining to the wavy current sheet as well as the modulation associated with this important heliospheric structure.
KeywordsCosmic rays Current sheet Heliosphere Drifts Stochastic differential equations
M.S. Potgieter expresses his gratitude for the partial funding granted by the South African National Research Foundation (NRF) under the Incentive and Competitive Grants for Rated Researchers. R.D. Strauss thanks the NRF for financial support under Thuthuka Programme, grant number 87998. J.L. Raath thanks the NRF and the South African Space Agency (SANSA) for partial financial support during his post-graduate study. J.L. Raath also thanks Dr. Andreas Kopp for discussions related to this research.
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