A simulation study of galactic proton modulation from solar minimum to maximum conditions

Ndiitwani, D. C.; Ngobeni, Donald; Aslam, O. P. M.; Bischoff, Driaan; Potgieter, M. S.; Boezio, M.; Munini, R.; Mikhailov, Vladimir

doi:10.22323/1.395.1327

Cited by 3 publications

(2 citation statements)

References 12 publications

(26 reference statements)

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“…Qualitatively, similar behaviour is shown as in Figure 2 but now it clearly illustrates how the time dependence differ below and above ~10 GV; below this value the MFPs decrease progressively and significantly from 2006-08 to 2013-15 but the opposite, and at a much smaller scale, occurs above this value. This seems counterintuitive, but similar behaviour (trends) using precise spectra from AMS-02, was reported also in [80,81,87] and implies that GCRs with R > 10 GV have somewhat smaller MFPs at solar minimum than at solar maximum; as such quite an interesting aspect of solar modulation at higher rigidity. In this context, it is well known that time trends in modulation is occurring differently at low and high rigidity during A > 0 and A < 0 cycles; see the discussion in [88,89], and references there-in, and recent modeling studies (e.g., [81]).…”

Section: Time Dependence Of the Diffusion Coefficientssupporting

confidence: 56%

A Perspective on the Solar Modulation of Cosmic Anti-Matter

Potgieter

Aslam

Bisschoff

et al. 2021

Physics

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Global modulation studies with comprehensive numerical models contribute meaningfully to the refinement of very local interstellar spectra (VLISs) for cosmic rays. Modulation of positrons and anti-protons are investigated to establish how the ratio of their intensity, and with respect to electrons and protons, are changing with solar activity. This includes the polarity reversal of the solar magnetic field which creates a 22-year modulation cycle. Modeling illustrates how they are modulated over time and the particle drift they experience which is significant at lower kinetic energy. The VLIS for anti-protons has a peculiar spectral shape in contrast to protons so that the total modulation of anti-protons is awkwardly different to that for protons. We find that the proton-to-anti-proton ratio between 1–2 GeV may change by a factor of 1.5 over a solar cycle and that the intensity for anti-protons may decrease by a factor of ~2 at 100 MeV during this cycle. A composition is presented of VLIS for protons, deuteron, helium isotopes, electrons, and particularly for positrons and anti-protons. Gaining knowledge of their respective 11 and 22 year modulation is useful to interpret observations of low-energy anti-nuclei at the Earth as tests of dark matter annihilation.

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Section: Time Dependence Of the Diffusion Coefficientssupporting

confidence: 56%

A Perspective on the Solar Modulation of Cosmic Anti-Matter

Potgieter

Aslam

Bisschoff

et al. 2021

Physics

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“…Usage of the 3D drift model of temporal modulation of galactic protons to compute proton spectra from 2009 to 2019, with changing solar activity levels, in comparison with observations from PAMELA and AMS02 was reported [98]. PAMELA and AMS observed a significant temporal changeability in the p/He ratios at rigidities below 3 GV.…”

Section: Pos(icrc2023)034mentioning

confidence: 96%

Rapporteur Talk: Solar and Heliospheric

Gil

2023

Proceedings of 38th International Cosmic Ray Conference — PoS(ICRC2023)

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This rapporteur paper summarizes the 127 contributions on solar and heliospheric physics (i.e. the SH sessions) presented during the 38th International Cosmic Ray Conference in Nagoya. Presented works covered a range of topics concerning updates on methods and instruments allowing cosmic rays measurements. Progress done in the modeling of modulation, acceleration and propagation of cosmic rays within the heliosphere was discussed. During the oral presentations and posters variety of topics were discussed. Among them there were deliberated such topics as changeability observed in the galactic cosmic rays (GCR) flux on the ground, i.e. GCR diurnal anisotropy, Forbush decreases, mid-and long-term GCR periodicities. Solar energetic particles (SEP) and ground level enhancements (GLEs) observational and modeling results were presented. Calculation of radiation dose for airplane passengers and crew, as well as astronaut, were reported. Moreover, historical reconstructions were discussed.

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A Numerical Study of the Solar Modulation of Galactic Protons and Helium from 2006 to 2017

Song¹,

Luo²,

Potgieter

et al. 2021

ApJS

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With continuous measurements from space-borne cosmic-ray detectors such as AMS-02 and PAMELA, precise spectra of galactic cosmic rays over the 11 yr solar cycle have become available. For this study, we utilize proton and helium spectra below 10 GV from these missions from 2006 to 2017 to construct a cosmic-ray transport model for a quantitative study of the processes of solar modulation. This numerical model is based on Parker’s transport equation, which includes four major transport processes. The Markov Chain Monte Carlo method is utilized to search the relevant parameter space related to the drift and the diffusion coefficients by reproducing and fitting the mentioned observed spectra. The resulting best-fit normalized χ 2 is mainly less than 1. It is found that (1) when reproducing these observations the parameters required for the drift and diffusion coefficients exhibit a clear time dependence, with the magnitude of the diffusion coefficients anticorrelated with solar activity; (2) the rigidity dependence of the resulting mean free paths varies with time, and their rigidity dependence at lower rigidity can even have a larger slope than at higher rigidity; (3) using a single set of modulation parameters for each pair of observed proton and helium spectra, most spectra are reproduced within observational uncertainty; and (4) the simulated proton-to-helium flux ratio agrees with the observed values in terms of its long-term time dependence, although some discrepancy exists, and the difference is mostly coming from the underestimation of proton flux.

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A simulation study of galactic proton modulation from solar minimum to maximum conditions

Cited by 3 publications

References 12 publications

A Perspective on the Solar Modulation of Cosmic Anti-Matter

A Perspective on the Solar Modulation of Cosmic Anti-Matter

Rapporteur Talk: Solar and Heliospheric

A Numerical Study of the Solar Modulation of Galactic Protons and Helium from 2006 to 2017

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