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Energetic Proton Propagation and Acceleration Simulated for the Bastille Day Event of 2000 July 14

Young, Matthew A. and Schwadron, Nathan A. and Gorby, Matthew and Linker, Jon and Caplan, Ronald M. and Downs, Cooper and Török, Tibor and Riley, Pete and Lionello, Roberto and Titov, Viacheslav and Mewaldt, Richard A. and Cohen, Christina M. S. (2021) Energetic Proton Propagation and Acceleration Simulated for the Bastille Day Event of 2000 July 14. Astrophysical Journal, 909 (2). Art. No. 160. ISSN 0004-637X.

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This work presents results from simulations of the 2000 July 14 ("Bastille Day") solar proton event. We used the Energetic Particle Radiation Environment Model (EPREM) and the CORona-HELiosphere (CORHEL) software suite within the SPE Threat Assessment Tool (STAT) framework to model proton acceleration to GeV energies due to the passage of a CME through the low solar corona, and we compared the model results to GOES-08 observations. The coupled simulation models particle acceleration from 1 to 20 R⊙, after which it models only particle transport. The simulation roughly reproduces the peak event fluxes and the timing and spatial location of the energetic particle event. While peak fluxes and overall variation within the first few hours of the simulation agree well with observations, the modeled CME moves beyond the inner simulation boundary after several hours. The model therefore accurately describes the acceleration processes in the low corona and resolves the sites of most rapid acceleration close to the Sun. Plots of integral flux envelopes from multiple simulated observers near Earth further improve the comparison to observations and increase potential for predicting solar particle events. Broken power-law fits to fluence spectra agree with diffusive acceleration theory over the low energy range. Over the high energy range, they demonstrate the variability in acceleration rate and mirror the interevent variability observed in solar cycle 23 ground-level enhancements. We discuss ways to improve STAT predictions, including using corrected GOES energy bins and computing fits to the seed spectrum. This paper demonstrates a predictive tool for simulating low-coronal solar energetic particle acceleration.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Young, Matthew A.0000-0003-2124-7814
Schwadron, Nathan A.0000-0002-3737-9283
Linker, Jon0000-0003-1662-3328
Caplan, Ronald M.0000-0002-2633-4290
Downs, Cooper0000-0003-1759-4354
Török, Tibor0000-0003-3843-3242
Riley, Pete0000-0002-1859-456X
Lionello, Roberto0000-0001-9231-045X
Titov, Viacheslav0000-0001-7053-4081
Mewaldt, Richard A.0000-0003-2178-9111
Cohen, Christina M. S.0000-0002-0978-8127
Additional Information:© 2021. The American Astronomical Society. Received 2020 December 14; revised 2021 January 20; accepted 2021 January 21; published 2021 March 15. This work was supported by NASA under the LWS (grant No. 80NSSC19K0067), O2R (grant No. 80NSSC20K0285), and SBIR/STTR programs, by the NSF PREEVENTS program (ICER1854790), and AFOSR (contract No. FA9550-15-C-0001). Computational resources were provided by NASA's NAS (Pleiades) and NSF's XSEDE (TACC & SDSC). Simulation output files containing the data for all streams shown in Figures 5 and 7, as well as interactive figure panels, are archived at The authors thank the reviewer for thoughtful comments and suggestions.
Funding AgencyGrant Number
Small Business Innovation Research (SBIR)UNSPECIFIED
Small Business Technology Transfer (STTR)UNSPECIFIED
Air Force Office of Scientific Research (AFOSR)FA9550-15-C-0001
Subject Keywords:Solar energetic particles; Solar activity; Solar coronal mass ejections; Solar storm
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Solar energetic particles (1491); Solar activity (1475); Solar coronal mass ejections (310); Solar storm (1526)
Record Number:CaltechAUTHORS:20210325-100425130
Persistent URL:
Official Citation:Matthew A. Young et al 2021 ApJ 909 160
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108553
Deposited By: Tony Diaz
Deposited On:25 Mar 2021 17:54
Last Modified:25 Mar 2021 17:54

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