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Abstract
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.
Highlights
Perspective on the Solar ModulationGalactic anti-matter, positrons and anti-protons, has been observed onEarth simultaneously, continuously and with high precision over prolonged periods of time by PAMELA [1,2,3] and AMS-02 [4,5]
Determination of the averaged values for modulation parameters that vary with solar activity is an important part of the modeling approach, the tilt angle α of the heliospheric current sheet (HCS) and the magnitude B of the heliospheric magnetic field (HMF), both considered as good proxies for solar activity when it comes to charged particles; see [60,61]
Since we focus on the refinements of very local interstellar spectra (VLISs) to be used in heliospheric modulation models, no discussion on how astrophysical aspects can change LISs and how that relates to the VLIS specified at the HP is done here
Summary
Aslam 2 , Driaan Bisschoff 2,3 and Donald Ngobeni 2,3.
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