Time dependence of electron and positron fluxes measured with the AMS-02 spectrometer

The electrons (e-) and positrons (e+) are a rare component of Cosmic Rays (CRs) since they constitute respectively only a 1% and 0.1% of cosmic radiation. However, the correct detection of e+- covers a great importance in the astrophysics field since, unlike the hadronic component, they are subjected to strong energy losses through the interaction with Interstellar Medium. As consequence e with energies above GeV that reach the Earth are galactic, with the source inside Kpc and through the study of their primary spectra it is possible to probe the local interstellar medium (LIS) and to indirectly detect new possible sources like pulsar or dark matter. However, these spectra, when measured near Earth, are significantly affected by the solar activity and we have the so-called solar modulation of CRs (SM). The solar activity has a cycle which period is ~11 years, during which it increases reaching a maximum and then decreases again. The intensity of cosmic ray radiation is correlated (or rather anticorrelated) with the activity of the sun. In order to have a correct understanding of LIS primary spectra of e+-, the SM should be well known and taken into account. The study of variation in time of e fluxes is useful in order to develop and test different models of the SM effects based on the interaction of cosmic rays with the heliosphere and can be used for the study of charge-sign dependent modulation. Before PAMELA and AMS-02, the charge-sign dependent SM was mostly studied comparing “all electrons”, which was actually the sum of e- and e+, with CR protons and helium of the same rigidity. However, only simultaneous measurements of e- and e+ (protons and anti-protons) over a complete solar activity cycle can represent a crucial test of the current charge-sign dependent modulation models. It is expected that the effects of drifts on CRs should become more evident closer to minimum solar activity. In this contest, AMS can provide the most accurate measurements of the time dependence of electron and positron fluxes since 2011 thanks to its high acceptance and the excellent performances of the detector. Anno iscrizione