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What is Causing the Deficit of High-Energy Solar Particles in Solar Cycle 24?

Mewaldt, R. A. and Li, G. and Hu, J. and Cohen, C. M. S. (2017) What is Causing the Deficit of High-Energy Solar Particles in Solar Cycle 24? In: 35th International Cosmic Ray Conference - ICRC2017. Proceedings of Science. No.301. SISSA , Trieste, Italy, Art. No. 111. http://resolver.caltech.edu/CaltechAUTHORS:20180828-122924747

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Abstract

The number of large Solar Energetic Particle (SEP) events in solar cycle 24 is reduced by a factor of about 2 compared to cycle 23. In the first 8 years of this cycle there have been only 38 “GOES” proton events compared to 79 at this point of cycle 23. What is less well known is that the fluence of protons and heavier ions is reduced by even greater factors (by 6 times for greater than 10 MeV protons, and by 9 times for greater than 100 MeV protons). Indeed the spectral breaks for H, O, and Fe are all occurring about 3 times lower in energy/nucleon in cycle 24. This talk will investigate the reduced acceleration efficiency in cycle 24 by simulating SEP acceleration using the Particle Acceleration and Transport in the Heliosphere (PATH) model, and an improved version known as iPATH, which simulates SEP acceleration at a CME-driven shock in two dimensions. Specifically, we will investigate how SEP fluences and energy spectra depend on variables that include the interplanetary magnetic field strength and turbulence level, and the density and spectrum of suprathermal seed particles.


Item Type:Book Section
Related URLs:
URLURL TypeDescription
https://doi.org/10.22323/1.301.0111DOIArticle
ORCID:
AuthorORCID
Mewaldt, R. A.0000-0003-2178-9111
Cohen, C. M. S.0000-0002-0978-8127
Additional Information:Copyright owned by the author(s) under the term of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. Work at Caltech and the University of Alabama/Huntsville was funded by a SHINE Collaborative Research grant under NSF Grant 1622487. In addition, Caltech was funded in part by NASA grants NNZ13AH66G and NNX15AG09G, and UA Huntsville was funded in part by NSF grant AGS-1622391, NASA grants NNX15AJ93G and NNX14AC08G, and by a 2013-2014 IIDR grant at UAH.
Group:Space Radiation Laboratory
Funders:
Funding AgencyGrant Number
NSFAGS-1622487
NASANNZ13AH66G
NASANNX15AG09G
NSFAGS-1622391
NASANNX15AJ93G
NASANNX14AC08G
University of Alabama in HuntsvilleUNSPECIFIED
Record Number:CaltechAUTHORS:20180828-122924747
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20180828-122924747
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:89231
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:29 Aug 2018 20:57
Last Modified:29 Aug 2018 20:57

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