Observation of Complex Time Structures in the Cosmic-Ray Electron and Positron Fluxes with the Alpha Magnetic Spectrometer on the International Space Station

Abstract

We present high-statistics, precision measurements of the detailed time and energy dependence of the primary cosmic-ray electron flux and positron flux over 79 Bartels rotations from May 2011 to May 2017 in the energy range from 1 to 50 GeV. For the first time, the charge-sign dependent modulation during solar maximum has been investigated in detail by leptons alone. Based on 23.5×10^{6} events, we report the observation of short-term structures on the timescale of months coincident in both the electron flux and the positron flux. These structures are not visible in the e^{+}/e^{-} flux ratio. The precision measurements across the solar polarity reversal show that the ratio exhibits a smooth transition over 830±30 days from one value to another. The midpoint of the transition shows an energy dependent delay relative to the reversal and changes by 260±30 days from 1 to 6 GeV.

Cosmic-ray interactions with the Sun using the fluka code

“…[51]. We also use the AMS-02 spectra measured for different Bartels' rotations (BRs) [52,53]. 5 Since the AMS-02 spectra are available starting from about 0.4 GeV/n, we have extrapolated the data down to 0.1 GeV/n by fitting the measured intensities with a function given by [54]: 4 We use the total intensity of electrons and positrons, and we refer to them as electrons.…”

“…[4,56]. In addition, the AMS-02 detector on the International Space Station started its operations only in May 2011 and, at present, their data are available until May 2017 [52,53]. Therefore, with the simulation set-up that we have implemented for this work, we are not able to make predictions on the gamma-ray flux in the period corresponding to the analysis of Ref.…”

Time-Dependent AMS-02 Electron-Positron Fluxes in an Extended Force-Field Model

“…In order to verify the validity of the approximations made in deriving eqs. (15) and (16), we have solved the transport eq. (1) directly using our own 2D finite-difference code that is similar in structure to the one by Langer [7].…”

“…Given the fully numerical code and the heliospheric model described above, we can check the validity of the assumption made in deriving eq. (15). The most fundamental one is the neglect of the adiabatic term in the transport equation (1).…”

“…The resulting modulated fluxes for one exemplary Bartels rotation is shown in Fig. 1 and compared to AMS-02 [15] data. We also show the results from the conventional force-field model.…”