23rd Annual NASA Space Radiation Investigators' Workshop (2012)
8002.pdf
Recent Updates to HZETRN – Coupled Meson and Lepton Transport
R. B. Norman1, T. C. Slaba2, and S. R. Blattnig2
1
University of Tennessee, Knoxville, TN, 2NASA Langley Research Center, Hampton, VA
An accurate understanding of the physical interactions and transport of space radiation is important for safe and
efficient space operations. Secondary particles produced by primary particle interactions with intervening materials
are an important contribution to radiation risk. Pions are copiously produced in the nuclear interactions typical of
space radiations and can therefore be an important contribution to radiation exposure. Charged pions decay almost
exclusively to muons while neutral pions decay to a pair of photons. Muons and photons then initiate
electromagnetic cascades through decay and interaction with intervening material. In this work, the NASA space
radiation transport code HZETRN has been extended to include the transport of pions, muons, electrons, positrons,
and photons. Muon, electron, and positron production in the Earth’s upper atmosphere is then investigated, and
comparisons with recent balloon flight measurements of differential flux are presented. The contribution to dose
from these secondary particles is also investigated.