Observations of Forbush Decreases of Cosmic-Ray Electrons and Positrons with the Dark Matter Particle Explorer

Abstract

The Forbush decrease (FD) represents the rapid decrease of the intensities of charged particles accompanied with the coronal mass ejections or high-speed streams from coronal holes. It has been mainly explored with the ground-based neutron monitor network, which indirectly measures the integrated intensities of all species of cosmic rays by counting secondary neutrons produced from interaction between atmospheric atoms and cosmic rays. The space-based experiments can resolve the species of particles but the energy ranges are limited by the relatively small acceptances except for the most abundant particles like protons and helium. Therefore, the FD of cosmic-ray electrons and positrons have just been investigated by the PAMELA experiment in the low-energy range (<5 GeV) with limited statistics. In this paper, we study the FD event that occurred in 2017 September with the electron and positron data recorded by the Dark Matter Particle Explorer. The evolution of the FDs from 2 GeV to 20 GeV with a time resolution of 6 hr are given. We observe two solar energetic particle events in the time profile of the intensity of cosmic rays, the earlier, and weaker, one has not been shown in the neutron monitor data. Furthermore, both the amplitude and recovery time of fluxes of electrons and positrons show clear energy dependence, which is important in probing the disturbances of the interplanetary environment by the coronal mass ejections.

Unfolding Drift Effects for Cosmic Rays over the Period of the Sun’s Magnetic Field Reversal

“…Apart from AMS observations distinguishing between GCRs particles according to their charge and mass, they are available up to very high rigidity (Aguilar et al 2021). Moreover, longduration space-based experiments with sophisticated detectors also resolve GCR species and their isotopic composition over a wide range of rigidity with a relatively high time resolution, for example, PAMELA (Adriani et al 2017), AMS (Aguilar et al 2021), and DAMPE (Alemanno et al 2021). Resolving the charge of GCRs is particularly helpful for studies of chargesign-dependent modulation over extended periods of time, which is what we focus on, especially over the HMF polarity reversal phase of Solar Cycle 24.…”

DArk Matter Particle Explorer: 7 years in Space

“…In particular, we focus on the Cosmic-Ray Electron (CRE) spectrum at low energies modulated by FD events (Figure 12 left-hand side panels). In 2021, an article based on one FD event detected by DAMPE in September 2017 was published [48]. Updated (preliminary) results based on 3 FD events (two in 2017 and one in 2021) were presented at this conference [49].…”

Properties of Forbush Decreases with AMS-02 Daily Proton Flux Data

“…They also show that the helium and the proton amplitude are in agreement within the errors for each rigidity interval from 1 to 10 GV, which suggests that the exponential description of the rigidity dependence might be extrapolated to helium to some degree. Alemanno et al (2021) studied the 2017 September FD event with the CRE (cosmic-ray electron and positron) fluxes observed by the Dark Matter Particle Explorer (DAMPE) and also found that the amplitude can be well described by an exponential function in terms of energies. Thus, the rigidity dependence of FDs remains a very complicated problem and needs to be further studied.…”