First observations of solar halo gamma rays over a full solar cycle
Linden T, Li JT, Zhou B, John I, Crnogorčević M, Peter AH, Beacom JF (2025)
Publication Type: Journal article
Publication year: 2025
Journal
Book Volume: 112
Pages Range: 1-21
Article Number: 103030
Journal Issue: 10
DOI: 10.1103/qm68-ng62
Abstract
We analyze 15 years of Fermi-LAT data and produce a detailed model of the Sun’s inverse-Compton scattering emission (solar halo), which is powered by interactions between ambient cosmic-ray electrons and positrons with sunlight. By developing a novel analysis method to analyze moving sources, we robustly detect the solar halo at energies between 31.6 MeV and 100 GeV, and angular extensions up to 45° from the Sun, providing new insight into spatial regions where there are no direct measurements of the Galactic cosmic-ray flux. The large statistical significance of our signal allows us to subdivide the data and provide the first γ-ray probes into the time variation and azimuthal asymmetry of the solar modulation potential, finding time-dependent changes in solar modulation both parallel and perpendicular to the ecliptic plane. Our results are consistent with (but with independent uncertainties from) local cosmic-ray measurements, unlocking new probes into astrophysical processes near the solar surface.
Involved external institutions
Stockholm University / Stockholms universitet
Sweden (SE)
University of Turin / Università degli Studi di Torino (UNITO)
Italy (IT)
Ohio State University
United States (USA) (US)
Fermi National Accelerator Laboratory (Fermilab)
United States (USA) (US)
Sweden (SE)
University of Turin / Università degli Studi di Torino (UNITO)
Italy (IT)
Ohio State University
United States (USA) (US)
Fermi National Accelerator Laboratory (Fermilab)
United States (USA) (US)
How to cite
APA:
Linden, T., Li, J.T., Zhou, B., John, I., Crnogorčević, M., Peter, A.H., & Beacom, J.F. (2025). First observations of solar halo gamma rays over a full solar cycle. Physical Review D, 112(10), 1-21. https://doi.org/10.1103/qm68-ng62
MLA:
Linden, Tim, et al. "First observations of solar halo gamma rays over a full solar cycle." Physical Review D 112.10 (2025): 1-21.
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