Simulations of the solar modulation of Helium isotopes constrained by observations

Ngobeni, Donald; Potgieter, M. S.; Aslam, O. P. M.; Bisschoff, Driaan; Ramokgaba, Innocentia; Ndiitwani, D. C.

doi:10.1016/j.asr.2021.12.018

Cited by 17 publications

(13 citation statements)

References 37 publications

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“…This trend is continued during the reversal phase as well, with intensities decreasing further to start the recovery consistently at the end of the reversal period. After the reversal period the higher rigidity particles recover somewhat sooner and faster than the low rigidity particles; in this context of an energy-dependent recovery, see also simulations by le Roux & Potgieter (1992) and Ngobeni et al (2022). The exercise is repeated in Figure 7(b) for electrons and in Figure 7(c) for positrons for the three kinetic energy ranges as indicated.…”

Section: Modulation Over the Polarity Reversalmentioning

confidence: 86%

“…These specific features and insights of the solar modulation of GCRs can only be gained by applying numerical models. In this context, see also the discussions based on numerical modeling by Zhao et al (2014) (2021), and on helium isotopes by Ngobeni et al (2022); for an overview, see Potgieter et al (2021).…”

Section: Discussionmentioning

confidence: 99%

“…We continue to apply our 3D drift-modulation model following the same methodology as before. The features of this particular model, as well as several applications inspired by GCR observations from various space missions, were extensively reported by Potgieter et al (2014, Vos & Potgieter (2016), , Aslam et al (2019), Aslam et al (2021), Ngobeni et al (2020), andNgobeni et al (2022) so that only the most essential aspects are repeated here. An important aspect about this type of GCR modeling is that we do not change the features of the model or the main assumptions from one application to another but rather assure a consistency so that results can be compared directly.…”

Section: Modulation Modelmentioning

confidence: 99%

“…We assume d ⊥θ = 6 for the period before the solar polarity reversal, then gradually change it to 9.0 in the case of electrons and positrons, but keep d ⊥θ = 6 for the whole period in the case of protons and antiprotons. For a visualization of this latitudinal dependence, see Figure 1 by Ngobeni & Potgieter (2012); for motivation and a first application, see Potgieter (2000), and for various other applications see also Ferreira et al (2003), Potgieter et al (2015), Nndanganeni & Potgieter (2016), Aslam et al (2019), Aslam et al (2021), andNgobeni et al (2022). For a detailed theoretical discussion of these aspects of the diffusion tensor and theory and the progress being made, see the extensive reviews by Shalchi (2009Shalchi ( , 2020.…”

Section: Model Specifics: Particle Drift and Diffusionmentioning

confidence: 99%

“…This is done by comparing our numerical simulations to available (published) GCR observations. See also recent complimentary modeling done by Corti et al (2019), Aslam et al (2019), Aslam et al (2021), Ngobeni et al (2020), andNgobeni et al (2022). Concerning the unfolding of drift effects and understanding how the major physical modulation processes for GCRs are changing from a negative to positive polarity through a period of uncertain polarity for Solar Cycle 24, we utilize proton, electron, and positron observations averaged over Bartels rotations (BRs) from the Alpha Magnetic Spectrometer (AMS; Aguilar et al 2018aAguilar et al , 2018b from 2011 May to 2015 May (BR numbers 2426-2480).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Unfolding Drift Effects for Cosmic Rays over the Period of the Sun’s Magnetic Field Reversal

Aslam¹,

Luo²,

Potgieter

et al. 2023

ApJ

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A well-established, comprehensive 3D numerical modulation model is applied to simulate galactic protons, electrons, and positrons from 2011 May to 2015 May, including the solar magnetic polarity reversal of Solar Cycle 24. The objective is to evaluate how simulations compare with corresponding Alpha Magnetic Spectrometer observations for 1.0–3.0 GV and what underlying physics follows from this comparison to improve our understanding of how the major physical modulation processes change, especially particle drift, from a negative to a positive magnetic polarity cycle. Apart from their local interstellar spectra, electrons and positrons differ only in their drift patterns, but they differ with protons in other ways such as adiabatic energy changes at lower rigidity. In order to complete the simulations for oppositely charged particles, antiproton modeling results are also obtained. Together, observations and corresponding modeling indicate the difference in the drift pattern before and after the recent polarity reversal and clarify to a large extent the phenomenon of charge-sign dependence during this period. The effect of global particle drift became negligible during this period of no well-defined magnetic polarity. The resulting low values of particles’ mean free paths (MFPs) during the polarity reversal contrast their large values during solar minimum activity and as such expose the relative contributions and effects of the different modulation processes from solar minimum to maximum activity. We find that the drift scale starts recovering just after the polarity reversal, but the MFPs keep decreasing or remain unchanged for some time after the polarity reversal.

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Section: Modulation Over the Polarity Reversalmentioning

confidence: 86%