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Cited by 24Solar and Space Plasma DynamicsAstrophysics and Cosmic PhenomenaIonosphere and magnetosphere dynamics

The DOI matches its Crossref record; 70 of the 70 references it cites were found in a registry or an index.

Long- and Short-term Variability of Galactic Cosmic-Ray Radial Intensity Gradients between 1 and 9.5 au: Observations by Cassini, BESS, BESS-Polar, PAMELA, and AMS-02

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Roussos, Elias, Dialynas, Konstantinos, Krupp, Norbert, Kollmann, Peter, Paranicas, Christopher, Roelof, Edmond C., Yuan, Chongjing, Mitchell, Donald G., Krimigis, Stamatios M.·2020·The Astrophysical Journal
DOI 10.3847/1538-4357/abc346
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Abstract

Spatial gradients of galactic cosmic-ray (GCR) fluxes are important for studying charged particle transport in the heliosphere. Little is known so far about how these gradients evolve with time. Here we present how the radial gradient (G r ) evolves between 2006 January and 2017 September using Cassini measurements of >300 MeV protons, which we combine with proton spectra obtained by advanced observatories at Earth (BESS, BESS-Polar, PAMELA, and AMS-02). All gradient calculations were performed for a nearly constant heliocentric distance of Cassini from Earth’s orbit and near the ecliptic, thus revealing only how G r changes with time. The variability patterns of G r are well established as they rely on a single data set for ∼9.5 au and accurately cross-calibrated GCR spectra for Earth at 1 au. We show that over solar-cycle timescales, G r is regulated by both the polarity of the solar magnetic field and the solar-cycle phase. During the negative-polarity phase (A < 0, 2006–2014), gradients are stronger and more stable with an average of G r = 3.5 ± 0.3%/au and with evidence of a minimum around the 2009 solar minimum. The gradient peaks at ∼4%/au around the solar maximum and subsequently experiences a gradual drop to ∼2%/au in the A > 0 phase (2014–2017). Regular G r enhancements over yearly or biennial timescales are also observed, in phase with quasi-biennial oscillations in GCR intensity. While all aforementioned results are based on Cassini measurements that are integral in energy, they are most representative for GCR protons in the low gigaelectronvolt range.

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  • The radial gradient of GCR flux is about 2-3.5% depending on solar cycle phase, using data at 1 and 9.5 au.

    “Roussos et al. (2020) found the radial gradient to be about 2-3.5% depending on the phase of the solar cycle using data at 1 and 9.5 au.”

    From Radiation environment for future human exploration on the surface of Mars: the current understanding based on MSL/RAD dose measurements (2021) · cites this paper as Roussos et al. 2020

    Section 4.3.2 reports an average gradient of 3.5 ± 0.3%/au in 2006–2014, falling to 2.0%/au by 2017. The Summary confirms that the analysis used observations between 1 and 9.5 au, but gives the gradient's usual range as 2–4%/au; the Abstract also reports a peak near 4%/au. Thus 2–3.5% captures the broad decline but understates the reported range and omits the per-au unit. (LLM, conf=0.85)

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Research works printed but not linked: 1

  1. Corti, 2019, Proc. ICRC, 36, 1070

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Metadata

Authors
Roussos, E., Dialynas, K., Krupp, N., Kollmann, P., Paranicas, C., Roelof, E. C., Yuan, C., Mitchell, D. G., & Krimigis, S. M.
Affiliations
  • Max Planck Institute for Solar System Research (DE)
  • Academy of Athens (GR)
  • Johns Hopkins University Applied Physics Laboratory (US)
  • Chinese Academy of Sciences (CN)
Corresponding author
Roussos, Elias
ORCID
Venue
The Astrophysical Journal
Publisher
American Astronomical Society
Published
2020-12-01
Volume
904
Issue
2
Pages
165
ISSN
  • 0004-637X (ISSN-L)
  • 1538-4357
DOI
10.3847/1538-4357/abc346
OpenAlex
W3107051079
Semantic Scholar
ec76c70e3094a8171b7e4417bf1b0965ab259dd4
Cited by
24
References
70
Citations by year
2026: 1 · 2025: 2 · 2024: 3 · 2023: 3 · 2022: 6 · 2021: 9
FWCI
2.01
Type
journal article
Language
en
Open access
Licence
Locations
The Astrophysical Journal (publishedVersion)
Funders
  • Deutsches Zentrum für Luft- und Raumfahrt (50 OH 1101, 50 OH 1502)
  • National Aeronautics and Space Administration (18-DRIVE18 2-0029)
Topics
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Solar and Space Plasma Dynamics
  • Physical Sciences › Physics and Astronomy › Nuclear and High Energy Physics › Astrophysics and Cosmic Phenomena
  • Physical Sciences › Earth and Planetary Sciences › Space and Planetary Science › Ionosphere and magnetosphere dynamics
Keywords
galactic cosmic rays, heliosphere, charged particle transport, solar cycle, solar magnetic field polarity, quasi-biennial oscillation, Cassini, battery energy storage, BESS-Polar, PAMELA, AMS-02, cosmic ray protons, heliocentric distance

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