University of New Hampshire University of New Hampshire Scholars' Repository Doctoral Dissertations Student Scholarship Winter 2016 CHARACTERIZATION OF THE RADIATION ENVIRONMENT OF THE INNER HELIOSPHERE USING LRO/CRATER AND EMMREM Colin Joyce University of New Hampshire, Durham Follow this and additional works at: https://scholars.unh.edu/dissertation Recommended Citation Joyce, Colin, "CHARACTERIZATION OF THE RADIATION ENVIRONMENT OF THE INNER HELIOSPHERE USING LRO/CRATER AND EMMREM" (2016). Doctoral Dissertations. 2269. https://scholars.unh.edu/dissertation/2269 This Dissertation is brought to you for free and open access by the Student Scholarship at University of New Hampshire Scholars' Repository. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of University of New Hampshire Scholars' Repository. For more information, please contact [email protected]. CHARACTERIZATION OF THE RADIATION ENVIRONMENT OF THE INNER HELIOSPHERE USING LRO/CRATER AND EMMREM BY Colin J. Joyce BS in Physics, University of New Hampshire, 2011 DISSERTATION Submitted to the University of New Hampshire in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Physics December, 2016 This dissertation has been examined and approved in partial fulfillment of the requirements for the degree of PhD in Physics by: Dissertation Director, Nathan A. Schwadron, Professor of Physics Charles W. Smith, Research Professor of Space Science Harlan Spence, Director of EOS Peter F. Bloser, Research Associate Professor of Space Science Per Berglund, Professor of Physics On 11/18/16 Original approval signatures are on file with the University of New Hampshire Graduate School. ii To Stefani iii Acknowledgements: I would like to begin by thanking my thesis committee for nominating me and providing excellent feedback and advice. In particular, I would like to thank my graduate advisor, Dr. Schwadron, for providing so many opportunities to be involved in diverse and exciting research and supplying guidance and inspiration whenever they were needed. I also owe a great deal to my undergraduate advisor, Dr. Smith, who got me started in space physics research and from whom I have learned so much over the years. I would also like to thank the CRaTER team, an amazing group of people that I have been very fortunate to work with during my time as a graduate student and who have been a constant source of help and guidance. Support for this work was provided by the NASA Lunar Reconnaissance Orbiter Project (NASA contract NNG11PA03C), as well as various NASA grants (EMMREM, grants NNX11AC06G and NNX07AC14G; C-SWEPA, grant NNX07AC14G; DoSEN, grant NNX13AC89G; DREAM, grant NNX10AB17A; and DREAM2; grant NNX14AG13A) and an NSF grant (Sun-2-Ice, grant AGS1135432). The CRaTER data used here is available on the CRaTER website: http://crater-web.sr.unh.edu/. The PREDICCS data used here is available on the PREDICCS website: http://prediccs.sr.unh.edu/. Family is the most important thing to me in the world and I can definitively state that I would not have been able to complete this journey without their support. First of all, I need to thank my mom for always being there for me, as well as instilling me with a curious mind and a willingness, possibly a need, to question authority. I believe these traits to be essential to any aspiring scientist. Much like how steel is formed at extreme temperatures, strong bonds often result from difficult conditions. Though we fought like hell growing up, we are forever linked by our common experiences and the relationship I have developed with my brother Will in recent years has been incredibly meaningful to me. I also must thank my aunt and uncle, Pam and Fred, for their continued interest and enthusiasm for my work. I do not make friends easily, but I have been very lucky to have a small clique of friends, Bubar, iv Iain, Jeff, Julia, Tony and Webber, that are like family to me. I couldn’t have gotten through graduate school without a sense of humor and I thank them for the many laughs we have shared over the years. My family has grown much larger in recent years, and in particular, I thank my wife’s parents, Andrea and Rick, for being so welcoming and inclusive of me over the years. It took them a little while to warm up to the quiet, long-haired teenager that showed up on their doorstep some eleven years ago wearing a ratty, duct-taped jean jacket, but I cannot express how proud I am to have become a member of their family Finally, and most importantly, I must thank my wife, Stefani, who has suffered with me through this long process and who has provided me with unwavering support, encouragement and above all else, patience. Like everything else I’ve done, this one is for her. v Contents Dedication iii Acknowledgements v List of acronyms: ix Abstract xi 1 Introduction 1 1.1 Motivation..................................... 1 1.2 Overview...................................... 3 2 Background 6 2.1 RadiationandSpaceWeather .......................... 6 2.1.1 RadiationEffects ............................. 10 2.1.2 Radiation Quantities . 10 2.1.3 Tissue and Organ Proxies Used in Radiation Risk Assessment . 14 2.1.4 Shielding . 15 2.2 Energetic Particles: Their Origins and Properties . ... 16 2.2.1 GalacticCosmicRays .......................... 18 2.2.2 Solar Energetic Particles . 24 2.2.3 Solar Flares and Magnetic Reconnection . 27 2.2.4 Coronal Mass Ejections and Shock Acceleration . 29 2.3 The Cosmic Ray Telescope for the Effects of Radiation . ... 34 2.4 The PREDICCS System and the EMMREM Radiation Model . 40 vi 2.4.1 Solving Particle Transport Using EPREM . 42 2.4.2 Computing Dosimetric Quantities Using BRYNTRN, HZETRN and HETC-HEDS ............................... 43 2.5 The state of radiation risk assessment during the Apollo era . ..... 45 3 Validation of PREDICCS 50 3.1 PREDICCS/CRaTER Comparison During SEP Events . 51 3.1.1 JanuarySEPEvent............................ 53 3.1.2 MarchSEPEvent............................. 55 3.1.3 MaySEPEvent.............................. 59 3.2 Discussion of CRaTER/PREDICCS Discrepancies During Events . .... 61 3.3 ValidationSummary ............................... 65 4 Analysis of the Radiation Hazard of the 2012 STEREO A ICME Event 71 4.1 Computed dose rates at STEREO A during the 23 July 2012 event and com- parisontopreviousevents ............................ 74 4.2 Assessing the Longitudinal Variation of the Radiation Impact . ..... 79 4.3 Summary of Radiation Modelling of 23 July 2012 Solar Event . 84 5 Characterization of the Atmospheric Radiation Environments of the Earth and Mars 87 5.1 Calculation of the Modulation Potential of GCRs Over the Course of the LRO Mission ...................................... 89 5.2 Modelling GCR Radiation in Earth’s Atmosphere with Comparisons to Bal- loonandAirlineBasedMeasurements. 92 5.3 Computation of Atmospheric Dose and Equivalent Dose Rates at Mars . 103 5.4 Summary of Atmospheric Radiation Modelling . 107 6 Summary 110 vii BIBLIOGRAPHY 118 viii List of acronyms: ARMAS (Automated Radiation Measurements for Aerospace Safety)- program designed to provide atmospheric radiation measurements using instruments on commercial and research aircraft BFO (Blood Forming Organ)- a tissue type used in radiation hazard assessment that is equivalent to bone marrow BRYNTRN (Baryon Transport Module)- a module used by EMMREM that uses the Boltz- mann equation to solve for the propagation of protons and their secondaries through shielding and compute radiation quantities CRaTER (Cosmic Ray Telescope for the Effects of Radiation)- an instrument on LRO designed to measure the energy deposited by energetic particles and characterize the lunar radiation environment EMMREM (Earth-Moon-Mars Radiation Environment Module)- a radiation model that solves for transport of energetic particles through the heliosphere and shielding materials, computing radiation quantities for various tissue types EPREM (Energetic Particle Radiation Environment Module)- the module used by EMM- REM that uses the focused transport equation to solve for the propagation of energetic particles through the heliosphere HETC-HEDS (High Energy Transport Code)- a Monte Carlo energetic particle transport code used here to transport GCRs through the Earth’s atmosphere HZETRN (High-Charge and Energy Transport Computer Program)- a program that uses the Boltzmann equation to solve for the transport of energetic particles, used here to trans- port GCRs through Mar’s atmosphere ICRP (International Commission on Radiological Protection)- organization which sets ra- ix diation limits and recommends guidelines for radiation safety ICRU (International Commission on Radiation Units and Measurements)- sister organiza- tion to the ICRP which defines units for radiation protection LET (Linear Energy Transfer)- the energy deposited in a material by an energetic particle divided by the path length through the material LRO (Lunar Reconnaissance Orbiter)- a spacecraft orbiting the Moon with a suite of in- struments including CRaTER PELs (Permissible Exposure Limits)- radiation limits for astronauts set by NASA PREDICCS (Predictions of radiation from REleASE, EMMREM, and Data Incorporating CRaTER, COSTEP, and other SEP measurements)- online system that provides modelled near real-time radiation data for the Earth, Moon and Mars RBE (Relative Biological Effectiveness)- a weighting factor based on radiation type for com- puting the gray-equivalent dose STEREO A/B (Solar TErrestrial RElations