The solar modulation of protons and anti-protons

Abstract

A comprehensive, three-dimensional drift model is used to study the solar modulation of cosmic ray protons and particularly of anti-protons. Spectra for protons and anti-protons from 10 MeV to 70 GeV are computed based on revisited local interstellar spectra for these particles. This is done for a complete solar cycle from 2006 to 2017, which includes the prolonged deep solar minimum period of 2006-2009 and the magnetic polarity reversal period of Oct 2012 to April 2014. The study highlights the modulation differences between these particles and addresses the level of particle drifts that is required to explain in detail the observed ant-proton to proton ratio, especially for the reversal period.

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

“…This stirred up a series of modulation modelling studies in order to establish what adjustment need to be made as required in mathematical and numerical models with respect to the elements of the diffusion and drift tensor in the relevant transport equation in order to reproduce GCR observations at Earth. In this context, [4,5] modelled proton, electron and positron spectral features observed by PAMELA, whereas [6] studied the modelling of GCR protons and helium nuclei as observed by PAMELA between 2006 and 2009 in a very quiet heliosphere, and [7] modelled also proton and anti-proton observations obtained after 2011. This work extends on this approach and studies the modulation of galactic protons from 2006 until 2017, a period coinciding with solar activity changing from minimum to maximum conditions, including a HMF polarity reversal.…”

“…This study takes advantage of simultaneous and continuous observations of galactic protons from the PAMELA [10] and AMS02 [11] space experiments to achieve the objective of the study. Both [7,8] successfully computed time and charge-sign dependent modulation for the period that covers the previous long and unusual deep solar minimum activity and the recent maximum period. The mentioned studies investigated how the main modulation processes including particle drifts and the major diffusion coefficients had evolved during the period investigated and subsequently how the corresponding charge-sign dependent modulation had occurred.…”

A Perspective on the Solar Modulation of Cosmic Anti-Matter

“…The relationship between, e.g., λ and K is given then by K || = (v/3)λ || = (βc/3)λ || , similarly for K ⊥r ,K ⊥θ and K D . The rigidity dependence of the three relevant MFPs λ ,λ ⊥r ,λ ⊥θ and the drift scale λ D are shown in Figure 2 for positrons in the left panel and for anti-protons in the right panel for yearly averages from 2006 to 2017 as established in [45,60,66,67] in order to reproduce the corresponding observed electron and positron spectra, and the proton and anti-proton spectra at Earth. with the calculated 15-month smoothed moving averages (SMA; red dots) as applied in the model.…”

“…During an A < 0 phase, it is expected that the changing wavy HCS plays an important even dominant role in the modulation of positively charged particles, whereas for an A > 0 polarity phase the drift directions become reversed so that negatively charged particles encounter the HCS during their entry. [60,66,67]; shaded band as in Figure 4.…”

“…Utilizing the precise observations at the Earth, the VLISs for all GCRs may be fine-tuned based on the output of the modulation model at high rigidity. This procedure has been followed for protons [48], for total helium and separately for the two helium isotopes [48][49][50][51], as well as for electrons and positrons [45,60,67] and for protons and anti-protons [66].…”