Distinct Solar Energetic Particle Shock Intensity–Diffusion Coefficient Relationships in the Inner Heliosphere
Issued Date
2025-11-01
Resource Type
ISSN
20418205
eISSN
20418213
Scopus ID
2-s2.0-105028534862
Journal Title
Astrophysical Journal Letters
Volume
993
Issue
1
Rights Holder(s)
SCOPUS
Bibliographic Citation
Astrophysical Journal Letters Vol.993 No.1 (2025)
Suggested Citation
Cuesta M.E., Fraschetti F., Livadiotis G., Farooki H.A., Shen M.M., Khoo L.Y., Szalay J.R., Rankin J.S., McComas D.J., Mitchell D.G., Christian E.R., Mitchell J.G., Berland G.D., Cohen C.M.S., Leske R.A., Xu Z., Muro G.D., Pecora F., Ruffolo D., Matthaeus W.H., Giacalone J., Schwadron N.A., Desai M.I., Dayeh M.A., Bale S.D., Stevens M.L., Livi R. Distinct Solar Energetic Particle Shock Intensity–Diffusion Coefficient Relationships in the Inner Heliosphere. Astrophysical Journal Letters Vol.993 No.1 (2025). doi:10.3847/2041-8213/ae109c Retrieved from: https://repository.li.mahidol.ac.th/handle/123456789/114104
Title
Distinct Solar Energetic Particle Shock Intensity–Diffusion Coefficient Relationships in the Inner Heliosphere
Author(s)
Cuesta M.E.
Fraschetti F.
Livadiotis G.
Farooki H.A.
Shen M.M.
Khoo L.Y.
Szalay J.R.
Rankin J.S.
McComas D.J.
Mitchell D.G.
Christian E.R.
Mitchell J.G.
Berland G.D.
Cohen C.M.S.
Leske R.A.
Xu Z.
Muro G.D.
Pecora F.
Ruffolo D.
Matthaeus W.H.
Giacalone J.
Schwadron N.A.
Desai M.I.
Dayeh M.A.
Bale S.D.
Stevens M.L.
Livi R.
Fraschetti F.
Livadiotis G.
Farooki H.A.
Shen M.M.
Khoo L.Y.
Szalay J.R.
Rankin J.S.
McComas D.J.
Mitchell D.G.
Christian E.R.
Mitchell J.G.
Berland G.D.
Cohen C.M.S.
Leske R.A.
Xu Z.
Muro G.D.
Pecora F.
Ruffolo D.
Matthaeus W.H.
Giacalone J.
Schwadron N.A.
Desai M.I.
Dayeh M.A.
Bale S.D.
Stevens M.L.
Livi R.
Author's Affiliation
University of California, Berkeley
The University of Arizona
California Institute of Technology
Princeton University
University of Delaware
NASA Goddard Space Flight Center
The University of Texas at San Antonio
Harvard-Smithsonian Center for Astrophysics
University of New Hampshire Durham
Johns Hopkins University Applied Physics Laboratory
Southwest Research Institute
Faculty of Science, Mahidol University
Space Sciences Laboratory
Smithsonian Astrophysical Observatory
The University of Arizona
California Institute of Technology
Princeton University
University of Delaware
NASA Goddard Space Flight Center
The University of Texas at San Antonio
Harvard-Smithsonian Center for Astrophysics
University of New Hampshire Durham
Johns Hopkins University Applied Physics Laboratory
Southwest Research Institute
Faculty of Science, Mahidol University
Space Sciences Laboratory
Smithsonian Astrophysical Observatory
Corresponding Author(s)
Other Contributor(s)
Abstract
It has been inferred from theory that the spatial diffusion coefficient (κ) upstream of shocks is anticorrelated with the intensity of solar energetic particles (SEPs) at the shock (j<inf>shock</inf>) motivated by quasi-linear theory (QLT). This is because a lower κ along the magnetic field (κ<inf>∥</inf>) implies that particles are trapped for longer, providing more acceleration and resulting in a higher j<inf>shock</inf>. However, the simplest version of DSA predicts that j<inf>shock</inf> is determined by the source of the injected population at the shock and plasma density jump with no relation to κ for low-energy SEPs. Here, we identify the relationship between κ and j<inf>shock</inf>, whose form is unknown, using Parker Solar Probe observations of eight shocks within 1 au. We estimate a characteristic κ<inf>fit</inf> along the shock normal by fitting the upstream SEP intensity profiles with a 1D steady-state transport model for acceleration and escape assuming pitch-angle isotropy in the plasma frame. Also, we estimate κ<inf>∥</inf> based on the magnetic power spectral density using QLT for comparison with κ<inf>fit</inf>. Our results show that both quantities are anticorrelated with j<inf>shock</inf>. Instead of a uniform relationship between κ and j<inf>shock</inf>, we find distinct relationships appearing as potential power laws manifested across SEP events with no obvious radial dependence from 0.07 to 0.74 au. These relationships may be grouped by similar shock parameters (in terms of speed, strength, and orientation). Our findings raise questions about SEP transport and its radial dependence within 1 au and provide important observational constraints for models of shock-accelerated particles.