University of Oulu

Marcelli, N., Boezio, M., Lenni, A., Menn, W., Munini, R., Aslam, O. P. M., Bisschoff, D., Ngobeni, M. D., Potgieter, M. S., Adriani, O., Barbarino, G. C., Bazilevskaya, G. A., Bellotti, R., Bogomolov, E. A., Bongi, M., Bonvicini, V., Bruno, A., Cafagna, F., Campana, D., … Zampa, N. (2022). Helium fluxes measured by the pamela experiment from the minimum to the maximum solar activity for solar cycle 24. The Astrophysical Journal Letters, 925(2), L24.

Helium fluxes measured by the PAMELA experiment from the minimum to the maximum solar activity for solar cycle 24

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Author: Marcelli, N.1; Boezio, M.2,3; Lenni, A.2,3,4;
Organizations: 1University of Rome "Tor Vergata," Department of Physics, I-00133 Rome, Italy
2INFN, Sezione di Trieste, I-34149 Trieste, Italy;
3IFPU, I-34014 Trieste, Italy
4University of Trieste, Department of Physics, I-34100 Trieste, Italy
5Universitat Siegen, Department of Physics, D-57068 Siegen, Germany
6North-West University, Centre for Space Research, 2520 Potchefstroom, South Africa
7Institute for Experimental and Applied Physics, Christian-Albrechts University in Kiel, D-24118 Kiel, Germany
8University of Florence, Department of Physics, I-50019 Sesto Fiorentino, Florence, Italy
9INFN, Sezione di Florence, I-50019 Sesto Fiorentino, Florence, Italy
10University of Naples "Federico II", Department of Physics, I-80126 Naples, Italy
11INFN, Sezione di Naples, I-80126 Naples, Italy
12Lebedev Physical Institute, RU-119991, Moscow, Russia
13University of Bari, Department of Physics, I-70126 Bari, Italy
14INFN, Sezione di Bari, I-70126 Bari, Italy
15Ioffe Physical Technical Institute, RU-194021 St. Petersburg, Russia
16Heliophysics Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA
17Department of Physics, Catholic University of America, Washington DC, USA
18KTH, Department of Physics, and the Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre, SE-10691 Stockholm, Sweden
19INFN, Sezione di Rome "Tor Vergata," I-00133 Rome, Italy
20RIKEN, EUSO team Global Research Cluster, Wako-shi, Saitama, Japan
21IFAC, I-50019 Sesto Fiorentino, Florence, Italy
22MEPhI: National Research Nuclear University MEPhI, RU-115409, Moscow, Russia
24University of Oulu, 90570 Oulu, Finland
25INFN, Laboratori Nazionali di Frascati, Via Enrico Fermi 40, I-00044 Frascati, Italy
26Istituto Nazionale di Astrofisica, Fosso del cavaliere 100, I-00133 Roma, Italy
27University of Udine, Department of Mathematics, Computer Science and Physics Via delle Scienze, I-206, Udine, Italy
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.8 MB)
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Language: English
Published: IOP Publishing, 2022
Publish Date: 2022-05-06


Time-dependent energy spectra of galactic cosmic rays (GCRs) carry fundamental information regarding their origin and propagation. When observed at the Earth, these spectra are significantly affected by the solar wind and the embedded solar magnetic field that permeates the heliosphere, changing significantly over an 11 yr solar cycle. Energy spectra of GCRs measured during different epochs of solar activity provide crucial information for a thorough understanding of solar and heliospheric phenomena. The PAMELA experiment collected data for almost 10 years (2006 June 15–2016 January 23), including the minimum phase of solar cycle 23 and the maximum phase of solar cycle 24. In this paper, we present new spectra for helium nuclei measured by the PAMELA instrument from 2010 January to 2014 September over a three-Carrington-rotation time basis. These data are compared to the PAMELA spectra measured during the previous solar minimum, providing a picture of the time dependence of the helium-nuclei fluxes over a nearly full solar cycle. Time and rigidity dependencies are observed in the proton-to-helium flux ratios. The force-field approximation of the solar modulation was used to relate these dependencies to the shapes of the local interstellar proton and helium-nuclei spectra.

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Series: Astrophysical journal letters
ISSN: 2041-8205
ISSN-E: 2041-8213
ISSN-L: 2041-8205
Volume: 925
Issue: 2
Article number: L24
DOI: 10.3847/2041-8213/ac4787
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Funding: We acknowledge partial financial support from The Italian Space Agency (ASI). We also acknowledge support from Deutsches Zentrum fur Luft-und Raumfahrt (DLR), The Swedish National Space Board, The Swedish Research Council, The Russian Space Agency (Roscosmos), Russian Science Foundation No-20-72-10170, RFBR and Russian ministry of science. R.M. acknowledges partial financial support from the INFN grant “giovani,” project ASMDM.
Copyright information: © 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.