Solar modulation of cosmic ray positrons in a very quiet heliosphere

Potgieter, M. S.; Vos, E. E.; Bisschoff, Driaan; Raath, Jan-Louis; Boezio, M.

doi:10.22323/1.301.0044

Cited by 4 publications

(8 citation statements)

References 15 publications

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“…Solar-Heliospheric Physics D. Ruffolo 2014, which confirms a pattern of charge sign dependence observed during previous solar cycles (e.g., [22]), including results presented here for Solar Cycle 23 [59]. [78] stated that the record high cosmic ray proton flux in 2009 (near the time of sunspot minimum) was unexpected because that corresponded to qA < 0. The motivation for this statement can be seen from Figure 14.…”

Section: Pos(icrc2017)1113supporting

confidence: 89%

“…Usually A < 0 conditions led to lower proton fluxes, especially below 0.3 GeV, but during the record-high GCR maximum of 2009 the spectrum was much higher, despite the A < 0 conditions. This leads the authors to predict an even higher GCR maximum near the end of the present decade (from presentation by [78]). It is exciting that the two Voyager spacecraft continue to provide data as they explore the outer heliosphere and space beyond the heliopause.…”

Section: Pos(icrc2017)1113mentioning

confidence: 90%

“…Also, near every sunspot maximum, there is a solar magnetic polarity reversal, marking a transition between "qA−" and "qA+" modulation. As a result, solar modulation also exhibits a variation with the ∼22-year solar magnetic cycle (modified from presentation by [78]). Figure 13 summarizes the long-term solar modulation of the GCR flux, based on data from the NM at Hermanus, South Africa, the currently active NM with the longest running dataset (since 1957).…”

Section: Solar Modulation Of Galactic Cosmic Rays (32)mentioning

confidence: 99%

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Solar-Heliospheric Physics

Ruffolo¹

2017

Proceedings of 35th International Cosmic Ray Conference — PoS(ICRC2017)

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This rapporteur paper summarizes the 99 presentations on solar-heliospheric physics at the 35th International Cosmic Ray Conference. These spanned a dizzying array of physical phenomena, especially time-dependent phenomena associated with solar storms, the 27-day solar rotation, the ∼11-year sunspot cycle, and the ∼22-year solar magnetic cycle. There was also work on composition-dependent effects and cosmic ray anisotropy involving transport effects. Topics included ground-and space-based instrumentation, solar energetic particles from solar storms (ranging from keV-range seed particles to GeV-range accelerated particles), interplanetary transport of energetic particles, Earth's radiation environment (including space weather and other effects of cosmic rays at Earth), the sun shadow in TeV-range Galactic cosmic rays (GCRs), and solar modulation of GCRs with the sunspot cycle and solar magnetic cycle.

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Section: Pos(icrc2017)1113supporting

confidence: 89%

Section: Pos(icrc2017)1113mentioning

confidence: 90%

Section: Solar Modulation Of Galactic Cosmic Rays (32)mentioning

confidence: 99%

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Solar-Heliospheric Physics

Ruffolo¹

2017

Proceedings of 35th International Cosmic Ray Conference — PoS(ICRC2017)

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“…At the outer modulation boundary, r out = 120 AU, particle relative intensities are convolved with the LIS and an energy spectrum at Earth is obtained. For the purposes of this study, no modulation is assumed beyond the HP, so that the heliopause spectrum and the very LIS is synonymous (see Potgieter et al, 2013). A reflective inner modulation boundary is used at r in = 0.1 AU, so that any pseudo-particle for which r < r in is reflected back into the modulation volume, i.e.…”

Section: The Numerical Modulation Modelmentioning

confidence: 99%

The effects of magnetic field modifications on the solar modulation of cosmic rays with a SDE-based model

Raath

Potgieter

Strauss

et al. 2016

Advances in Space Research

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A numerical model for the solar modulation of cosmic rays, based on the solution of a set of stochastic differential equations, is used to illustrate the effects of modifying the heliospheric magnetic field, particularly in the polar regions of the heliosphere. To this end, the differences in the modulation brought about by each of three choices for the heliospheric magnetic field, i.e. the unmodified Parker field, the Smith-Bieber modified field, and the Jokipii-Kóta modified field, are studied. It is illustrated that both the Jokipii-Kóta and Smith-Bieber modifications are effective in modifying the Parker field in the polar regions. In addition, it is argued that the modification of Smith and Bieber is based on observational evidence and has a firm physical basis, while these motivations are lacking in the case of the Jokipii-Kóta modification. From a cosmic ray modulation point of view, we found the Smith-Bieber modification to be the most suitable choice for modifying the heliospheric magnetic field. The features and effects of these three modifications are illustrated both qualitatively and quantitatively. It is also shown how the Smith-Bieber modified field can be applied in cosmic ray modulation models to reproduce observational cosmic ray proton spectra from the PAMELA mission during the solar minimum of 2006 -2009. These results are compared with those obtained in previous studies of this unusual solar minimum activity period and found to be in good qualitative agreement.

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“…An example of this comprehensive approach to proton modulation is given in [39] and lately in [120]. The same model is then applied to GCR electrons as given in [111] and also positrons [135]. Once the model has reached this level of sophistication, it can be applied with confidence to predict the VLIS at the HP for positrons and anti-protons, in fact for all GCRs for which no observations exist beyond the HP as done in [121] with their HelMod approach.…”

Section: The Question Of Vliss At the Heliopausementioning

confidence: 99%

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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Solar modulation of cosmic ray positrons in a very quiet heliosphere

Cited by 4 publications

References 15 publications

Solar-Heliospheric Physics

Solar-Heliospheric Physics

The effects of magnetic field modifications on the solar modulation of cosmic rays with a SDE-based model

A Perspective on the Solar Modulation of Cosmic Anti-Matter

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