INFN Sez. Milano-Bicocca Final updates about "Observation of Fine Time Structures in the Cosmic Proton and Helium Fluxes" article. Stefano Della Torre INFN Sez. Milano-Bicocca
Analysis & manuscript preparation: Aachen, Perugia, KIT Prepared two parallel articles: Observation of Fine Time Structures in the Cosmic Proton and Helium Fluxes with the Alpha Magnetic Spectrometer on the International Space Station Observation of Complex Time Structures in the Cosmic-Ray Electron and Positron Fluxes with the Alpha Magnetic Spectrometer on the International Space Station Analysis & manuscript preparation: Hawaii, Milano, Perugia Analysis & manuscript preparation: Aachen, Perugia, KIT Article Timeline End November 2017, first submission to PRL End December 2017, referee reports: recommended publication after evision January-February 2018, revised version + response documents March 2018, resubmission goal 23/02/2018 AMS-Italy - S. Della Torre
AMS-Italy - S. Della Torre Fig. SM-1 We shows the detailed behavior of (a) the proton flux and (b) the helium flux as functions of time and of rigidity from 1 to 10 GV and from 2 to 10 GV, respectively. For completeness, Fig. SM-1 shows the entire rigidity range of proton and helium fluxes, along with their total variation from May 2011 to May 2017. As seen, both the proton and helium spectra exhibit large variations with time at low rigidities which decrease with increasing rigidity. Both fluxes have a minimum in February 2014. Fig. 1 23/02/2018 AMS-Italy - S. Della Torre
AMS-Italy - S. Della Torre Both the proton and helium fluxes have fine time structures each with maxima and minima with boundaries marked by the vertical dashed lines from I to X. The structures in the proton flux and the helium flux are nearly identical in both time and relative amplitude with the exception of boundary VI which is a minimum only for rigidities greater than 5 GV. Fig. 2 23/02/2018 AMS-Italy - S. Della Torre
AMS-Italy - S. Della Torre I (September 27, 2011), II (March 7, 2012), III (July 20, 2012), IV (May 13, 2013), and VII (March 19, 2015), have also been observed by AMS in the electron flux and the positron flux. After boundary VII, the amplitude of the structures are considerably reduced and the proton and helium fluxes steadily rise at all rigidities, also observed in the electron flux and the positron flux. Fig. 2 23/02/2018 AMS-Italy - S. Della Torre
AMS-Italy - S. Della Torre The data greatly improve the accuracy and the sensitivity of the time dependent proton and helium measurements FIG. 3. (a) the AMS proton flux for [1.19−1.40] GeV, SOHO/EPHIN for [1.12−1.29] GeV, (b) the AMS helium flux for [1.11−1.28] GeV/n 23/02/2018 AMS-Italy - S. Della Torre
AMS-Italy - S. Della Torre Above 3.29 GV the ratio is time independent. Below 3.29 GV the ratio has a longt-term time dependence, the ratio steadly decrease after Feb 28, 2015 ± 45 days 23/02/2018 AMS-Italy - S. Della Torre
The change of slope in p/He coincides with the rising phase of spectra 23/02/2018 AMS-Italy - S. Della Torre
AMS-Italy - S. Della Torre From our understanding of cosmic ray transport in the heliosphere, a non-constant p/He flux ratio may be due to several effects: (1) velocity dependence of the diffusion tensor, that appears at low-rigidity; (2) differences in the interstellar spectra; (3) He-3 and He-4 isotopic composition effects arising from (1) and (2). See Nicola's Talk 23/02/2018 AMS-Italy - S. Della Torre
AMS-Italy - S. Della Torre Conclusion The proton flux and the helium flux observed by AMS have fine time structures nearly identical in both time and relative amplitude. The amplitudes of the structures decrease with increasing rigidity and are observed up to 40 GV. After March 2015, the amplitude of the structures is considerably reduced and the proton and helium fluxes steadily rise at all rigidities. The p/He flux ratio above ∼3 GV is time independent. Remarkably, below ∼3 GV the ratio has a long-term time dependence coinciding with the period during which the fluxes start to rise. 23/02/2018 AMS-Italy - S. Della Torre