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Shock Connectivity and the Late Cycle 24 Solar Energetic Particle Events in July and September 2017

Luhmann, J. G. and Mays, M. L. and Li, Yan and Lee, C. O. and Bain, H. and Odstrcil, D. and Mewaldt, R. A. and Cohen, C. M. S. and Larson, D. and Petrie, Gordon (2018) Shock Connectivity and the Late Cycle 24 Solar Energetic Particle Events in July and September 2017. Space Weather, 16 (5). pp. 557-568. ISSN 1542-7390.

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As solar activity steadily declined toward the cycle 24 minimum in the early months of 2017, the expectation for major solar energetic particle (SEP) events diminished with the sunspot number. It was thus surprising (though not unprecedented) when a new, potentially significant active region rotated around the East limb in early July that by midmonth was producing a series of coronal eruptions, reaching a crescendo around 23 July. This series, apparently associated with the birth of a growing pseudostreamer, produced the largest SEP event(s) seen since the solar maximum years. Activity abated with the decay of the active region, but a second episode of magnetic flux emergence in the same area in early September initiated a new round of eruptions. The western longitude of the erupting region, together with its similar coronal setting in both cases, resulted in a set of nearly homologous multipoint SEP event periods at Earth, Solar TErrestrial RElations Observatory‐A and Mars (Mars Atmosphere and Volatile EvolutioN) for July and September 2017. We use a combination of WSA‐ENLIL‐cone heliospheric simulation results, together with SEPMOD SEP event modeling, to illustrate how the event similarities at the three observer sites can be understood from their relative positions and their connectivities to the generated interplanetary shocks.

Item Type:Article
Related URLs:
URLURL TypeDescription
Luhmann, J. G.0000-0003-0626-9353
Mays, M. L.0000-0001-9177-8405
Lee, C. O.0000-0002-1604-3326
Bain, H.0000-0003-2595-3185
Mewaldt, R. A.0000-0003-2178-9111
Cohen, C. M. S.0000-0002-0978-8127
Additional Information:© 2018 American Geophysical Union. Received 6 MAR 2018; Accepted 28 APR 2018; Accepted article online 6 MAY 2018; Published online 25 MAY 2018. The authors are grateful to the staff of the CCMC for their contributions to deriving the ENLIL cone model parameters, to the SOHO LASCO and STEREO SECCHI investigators for the coronagraph images used, to the GONG Observatory for providing the magnetic synoptic maps used for the ambient solar wind description, to the ACE and STEREO plasma investigation teams for providing 1‐AU solar wind data shown here, to the ACE EPAM and GOES EPS Instrument and data providers, and to the MAVEN and Venus Express projects for providing data for the planetary site SEP event‐model comparisons. This work was supported in part by NASA grant NNX15AG09G to the University of California, Berkeley for the STEREO‐IMPACT investigation and by NASA grant NNX15AUo1G to the University of New Hampshire for the STEREO PLASTIC investigation. Additional support for the Caltech contributions is from NSF grant 1156004. The model development at UC Berkeley is sponsored by the NSF Award 1322826 through the Living With a Star Program in cooperation with NASA. M. L. M., H. B., and Y. L. acknowledge the support of NASA LWS grant NNX15AB80G. WSA‐ENLIL+Cone simulation results have been provided by the Community Coordinated Modeling Center at the Goddard Space Flight Center through their public Runs on Request system (; run numbers Leila_Mays_080917_SH_1, Leila_Mays_120817_SH_9). The WSA model was developed by N. Arge at AFRL, and the ENLIL Model was developed by D. Odstrcil at GMU.
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Issue or Number:5
Record Number:CaltechAUTHORS:20180529-082911219
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Official Citation:Luhmann, J. G., Mays, M. L., Li, Y., Lee, C. O., Bain, H., Odstrcil, D., et al. (2018). Shock connectivity and the late cycle 24 solar energetic particle events in July and September 2017. Space Weather, 16, 557–568.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86647
Deposited By: Tony Diaz
Deposited On:29 May 2018 16:10
Last Modified:03 Oct 2019 19:46

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