Abstract
To understand solar energetic particle (SEP) events and their acceleration processes, it is important to study the SEP properties, e.g. duration and fluence. In this work, we analyzed the temporal evolution of fluxes [cm−2 sr−1 s−1] of >10, >30, and >60 MeV protons and the temporal and spectral evolution of electromagnetic-radiation components for 34 major SEP events that include 13 ground-level enhancement (GLE)-SEP and 21 non-GLE-SEP events, and then determined their possible onset and end times [UT], their duration [hours], and fluence [cm−2 sr−1]. It is observed that the temporal fluxes of >30 MeV protons can sometimes be utilized for those of the fluxes of >10 MeV protons. Correspondence between SEP duration and fluence demonstrates the dependence of fluence on duration that helps distinguish the typical and atypical SEP events. For instance, for the >10 MeV protons, correspondence between the duration and fluence exhibited a weaker correlation (\(r\approx \) 0.78; \(p\)<0.002) during the 13 GLE-SEPs than that (\(r \approx \) 0.83; \(p\)<0.0001) during the 21 non-GLE-SEPs, revealing a few GLE-SEPs with disproportionate comparability. During the 13 GLE-SEPs, correspondence between the SEP duration and fluence for >30 MeV protons exhibited a stronger correlation (\(r \approx \) 0.82; \(p\)<0.0006) than that (\(r \approx \) 0.78; \(p\)<0.002) for the >10 MeV protons, indicating that the temporal window of >30 MeV protons is sometimes more appropriate for obtaining a reasonable duration of SEPs. Accordingly, when the temporal window of flux of >30 MeV protons is utilized for that of the >10 MeV protons, the correlation increased significantly (\(r \approx \) 0.86; \(p\)<0.0002) during the 13 GLE-SEPs.
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Data Availability
The data used in this study are available in the CDAW-NASA, GOES-NOAA, OMNI-NASA, and Wind-WAVES. Authors thank the science teams of the spacecraft for keeping the data available in the sites.
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Acknowledgments
The authors would like to thank the anonymous reviewer for constructive comments and valuable suggestions that indeed developed the article significantly. Some discussions with Victor Grechnev (ISTP/RAS) on the difference between GLE-SEPs and non-GLE-SEPs, and particularly on the equations for longitude-corrected SEP fluence, are acknowledged.
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W.Q. Gan acknowledges the National Natural Science Foundation of China (U1731241, 11921003, and U1931138) and by the Chinese Academy of Sciences (XDA15052200). J. Rodríguez-Pacheco acknowledges the Spanish AEI project with reference: PID2019-104863RB-I00/AEI/10.13039/501100011033.
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Firoz, K.A., Gan, W.Q., Li, Y.P. et al. Duration and Fluence of Major Solar Energetic Particle (SEP) Events. Sol Phys 297, 71 (2022). https://doi.org/10.1007/s11207-022-01994-7
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DOI: https://doi.org/10.1007/s11207-022-01994-7