Time and Charge-Sign Dependence of the Heliospheric Modulation of Cosmic Rays

Abstract

Simultaneous and continuous observations of galactic cosmic-ray electrons and positrons from the PAMELA and AMS02 space experiments are most suitable for numerical modeling studies of the heliospheric modulation of these particles below 50 GeV. A well-established comprehensive three-dimensional modulation model is applied to compute full spectra for electrons and positrons with the purpose of reproducing the observed ratio positrons/electrons for a period which covers the previous long and unusual deep solar minimum activity and the recent maximum activity phase including the polarity reversal of the solar magnetic field. For this purpose the very local interstellar spectra for these particles were established first. Our study is focused on how the main modulation processes, including particle drifts, and other parameters such as the three major diffusion coefficients, had evolved, and how the corresponding charge-sign dependent modulation had occurred subsequently. The end result of our effort is the detailed reproduction of positron/electrons from 2006 to 2015, displaying both qualitative and quantitative agreement with the main observed features. Particularly, we determine how much particle drifts is needed to explain the time dependence exhibited by the observed positron/electron during each solar activity phase, especially during the polarity reversal phase when no well-defined magnetic polarity was found.

16 pages, 8 figures, Submitted to Astrophysical Journal

References in corpus (12)

• Observation of an anomalous positron abundance in the cosmic radiation
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• New very local interstellar spectra for electrons, positrons, protons and light cosmic ray nuclei
• Time dependence of the electron and positron components of the cosmic radiation measured by the PAMELA experiment between July 2006 and December 2015
• Global gradients for cosmic-ray protons in the heliosphere during the solar minimum of cycle 23/24
• New evidence for charge-sign dependent modulation during the solar minimum of 2006 to 2009
• Time dependence of the flux of helium nuclei in cosmic rays measured by the PAMELA experiment between July 2006 and December 2009
• Measurement of low-energy cosmic-ray electron and positron spectra at 1 AU with the AESOP-Lite spectrometer

Cited by in corpus (4)

• Modelling the transport of relativistic solar protons along a heliospheric current sheet during historic GLE events
• Unfolding Drift Effects for Cosmic Rays over the Period of the Sun's Magnetic Field Reversal
• Galactic Cosmic-Ray Propagation in the Inner Heliosphere: Improved Force-Field Model
• Modulation of cosmic ray anti-protons in the heliosphere: simulations for a solar cycle