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  1. On the Origin of the sudden Heliospheric Open Magnetic Flux Enhancement
    during the 2014 Pole Reversal

    S.G. Heinemann, M. J. Owens, M. Temmer, J. A. Turtle, C. N. Arge, C. J. Henney,
    J. Pomoell, E. Asvestari, J. A. Linker, C. Downs, R. M. Caplan, S. J. Hofmeister,
    C. Scolini, R. F. Pinto, and M. S. Madjarska
    The Astrophysical Journal. Accepted (2024). PDF (Coming Soon).
  2. Improved modelling of SEP event onset within the WSA–Enlil–SEPMOD framework
    E. Palmerio, J.G. Luhmann, L. M. Mays, R. M. Caplan, D. Lario, I.G. Richardson, K. Whitman,
    C.O. Lee, B. Sánchez-Cano, N. Wijsen, Y. Li, C. Cardoso, M. Pinto, D. Heyner, D. Schmid,
    H. Auster, and D. Fischer
    Journal of Space Weather and Space Climate. 14,3 (2024). PDF.


  1. Global MHD Simulations of the Time-dependent Corona
    R. Lionello, C. Downs, E. I. Mason, J. A. Linker, R. M. Caplan, V. S. Titov, and M. L. DeRosa
    The Astrophysical Journal. 959,77 (2023). PDF.
  2. Time-dependent Dynamics of the Corona
    E. I. Mason, R. Lionello, C. Downs, J. A. Linker, R. M. Caplan, and M. L. DeRosa
    Astrophysical Journal Letters. 959,L4 (2023). PDF.
  3. Deflection of Coronal Mass Ejections in Unipolar Ambient Magnetic Fields
    M. Ben-Nun, T. Torok, E. Palmerio, C. Downs, V. S. Titov, R. M. Caplan, and R. Lionello
    The Astrophysical Journal. 957,74 (2023). PDF.
  4. Improving Coronal Hole Detections and Open Flux Estimates
    R. M. Caplan, E. I. Mason, C. Downs, and J. A. Linker
    The Astrophysical Journal. 958,43 (2023). PDF.
  5. Acceleration of a production Solar MHD code with Fortran standard parallelism:
    From OpenACC to `do concurrent'

    R. M. Caplan, M. M. Stulajter, and J. A. Linker
    13th AsHES Workshop. 2023 IEEE IPDPSW Proceedings., (2023) 582-590. PDF.
  6. Review of Solar Energetic Particle Prediction Models
    K. Whitman, ..., R. M. Caplan, et. al.
    Advances in Space Research. 72 (2023) 5161-5242. PDF.


  1. Can Fortran's `do concurrent' Replace Directives for Accelerated Computing?
    M. M. Stulajter, R. M. Caplan, and J. A. Linker
    Accelerator Programming Using Directives. WACCPD 2021.
    Lecture Notes in Computer Science, 13194, 3-21 (2022). Springer, Cham. PDF.
  2. Comparing and Contrasting the Properties of the Inner Heliosphere
    for the Three Most Recent Solar Minima

    P. Riley, R. M. Caplan, C. Downs, J. A. Linker, and R. Lionello.
    JGR: Space Physics. 127,8 (2022) e2022JA030261. PDF.


  1. Coronal Hole Detection and Open Magnetic Flux
    J. A. Linker, S. G. Heinemann, M. Temmer, M. J. Owens, R. M. Caplan, C. N. Arge,
    E. Asvestari, V. Delouille, C. Downs, and S. J. Hofmeister.
    The Astrophysical Journal. 918,1 (2021) 21. PDF.
  2. Variations in Finite Difference Potential Fields
    R. M. Caplan, C. Downs, J. A. Linker, and Z. Mikic.
    The Astrophysical Journal. 915,1 (2021) 44. PDF.
  3. Using Parker Solar Probe observations during the first four perihelia to
    constrain global magnetohydrodynamic models

    P. Riley, R. Lionello, R. M. Caplan, C. Downs, J. A. Linker, S. Badman, and M. L. Stevens
    Astronomy & Astrophysics. 650 (2021) A19. PDF.
  4. Energetic Proton Propagation and Acceleration Simulated for the
    Bastille Day Event of July 14, 2000

    M. A. Young, N. A. Schwadron, M. Gorby, J. Linker, R. M. Caplan, C. Downs,
    T. Török, P. Riley, R. Lionello, V. Titov, R. A. Mewaldt, C. M. S. Cohen
    The Astrophysical Journal. 909,2 (2021) 160. PDF.


  1. Early Results from the Solar-minimum 2019 Total Solar Eclipse.
    J. M. Pasachoff, C. A. Lockwood, J. L. Inoue, E. N. Meadors, A. Voulgaris, D. Sliski, A. Sliski, K. P. Reardon,
    D. B. Seaton, R. M. Caplan, C. Downs, J. A. Linker, G. Schneider, P. Rojo, and A. C. Sterling.
    Proceedings of the International Astronomical Union. s354,15 (2020) 3-14 PDF.


  1. Can an Unobserved Concentration of Magnetic Flux Above the Poles of the Sun
    Resolve the Open Flux Problem?

    P. Riley, J. A. Linker, Z. Mikic, R. M. Caplan, C. Downs and J. Thumm.
    The Astrophysical Journal. 884,1 (2019) 18. PDF.
  2. Predicting the Structure of the Solar Corona and Inner Heliosphere
    during Parker Solar Probe's First Perihelion Pass.

    P. Riley, C. Downs, J. A. Linker, Z. Mikic, R. Lionello, and R. M. Caplan.
    The Astrophysical Journal. 874,2 (2019) L15. PDF.
  3. GPU Acceleration of an Established Solar MHD Code using OpenACC.
    R. M. Caplan, J. A. Linker, Z. Mikic, C. Downs, T. Torok, and V. S. Titov.
    Journal of Physics: Conference Series. ASTRONUM 2018. 1225,1 (2019) 012012 PDF.
  4. Coupled MHD-Focused Transport Simulations for Modeling Solar Particle Events.
    J. A. Linker, R. M. Caplan, N. Schwadron, M. Gorby, C. Downs, T. Torok, R. Lionello, and J. Wijaya
    Journal of Physics: Conference Series. ASTRONUM 2018. 1225,1 (2019) 012007 PDF.


  1. Predicting the Corona for the 21 August 2017 Total Solar Eclipse.
    Z. Mikic, C. Downs, J. A. Linker, R. M. Caplan, D. H. Mackay, L. A. Upton, P. Riley, R. Lionello,
    T. Torok, V. S. Titov, J. Wijaya, M. Druckmuller, J. M. Pasachoff, and W. Carlos.
    Nature Astronomy. 2 (2018) 913-921. ePDF.
  2. Sun-to-Earth MHD Simulation of the 14 July 2000 “Bastille Day” Eruption.
    T. Torok, C. Downs, J. A. Linker, R. Lionello, V. S. Titov,
    Z. Mikic, P. Riley, R. M. Caplan, and J. Wijaya
    The Astrophysical Journal. 858,1 (2018) 75. PDF.
  3. Regularized Biot-Savart Laws for Modeling Magnetic Flux Ropes.
    V. S. Titov, C. Downs, Z. Mikic, T. Torok, J. A. Linker, and R. M. Caplan
    The Astrophysical Journal Letters. 852,2 (2018) L21. PDF.


  1. The Open Flux Problem.
    J.A. Linker, R.M. Caplan, C. Downs, P. Riley, Z. Mikic, R. Lionello,
    C. J. Henney, C. N. Arge, Y. Liu, M. L. Derosa, A. Yeates, and M. J. Owens.
    The Astrophysical Journal. 848,1 (2017) 70. PDF.


  1. Advancing parabolic operators in thermodynamic MHD models:
    Explicit super time-stepping versus implicit schemes with Krylov solvers.

    R. M. Caplan, Z. Mikic, J. A. Linker, and R. Lionello.
    Journal of Physics: Conference Series. ASTRONUM 2016. 837,1 (2017) 012016 PDF.
  2. Synchronic coronal hole mapping using multi-instrument EUV images:
    Data preparation and detection method.

    R.M. Caplan, C. Downs, and J.A. Linker.
    The Astrophysical Journal. 823,1 (2016) 53. PDF.
  3. Properties of the Fast Forward Shock Driven by the July 23 2012 Extreme Coronal Mass Ejection.
    P. Riley, R.M. Caplan, J. Giacalone, D. Lario, and Y. Liu.
    The Astrophysical Journal. 819,1 (2016) 57. PDF.
  4. MHD Simulation of the Bastille Day Event.
    J.A. Linker, T. Torok, C. Downs, R. Lionello, V. Titov, R.M. Caplan, Z. Mikic, and P. Riley.
    AIP Conference Proceedings, Solar Wind 14. 1720, (2016) 020002. PDF.
  5. An Empirically Driven Time-Dependent Model of the Solar Wind.
    J. A. Linker, R.M. Caplan, C. Downs, R. Lionello, P. Riley, Z. Mikic, C.J. Henney, C.N. Arge, T. Kim, and N. Pogorelov.
    Journal of Physics: Conference Series. ASTRONUM 2015. 719,1 (2016) 012012 PDF.


  1. Scattering and Leapfrogging of Vortex Rings in a Superfluid.
    R.M. Caplan, J. D. Talley, R. Carretero-González, and P.G. Kevrekidis.
    Physics of Fluids. 26 (2014) 097101. PDF.
  2. A Modulus-Squared Dirichlet Boundary Condition for Time-Dependent
    Complex Partial Differential Equations and its Application to the Nonlinear Schrödinger Equation.

    R.M. Caplan and R. Carretero-González.
    SIAM Journal on Scientific Computing. 36,1 (2014) A1-A19 PDF.


  1. NLSEmagic: Nonlinear Schrödinger Equation Multidimensional Matlab-based
    GPU-accelerated Integrators using Compact High-order Schemes.

    R.M. Caplan.
    Computer Physics Communications. 184,4 (2013) 1250-1271. PDF.
  2. A Two-Step High-Order Compact Scheme for the Laplacian Operator and its
    Implementation in an Explicit Method for Integrating the Nonlinear Schrödinger Equation.

    R.M. Caplan and R. Carretero-González.
    Journal of Computational and Applied Mathematics. 251 (2013) 33-46. PDF.
  3. Numerical Stability of Explicit Runge-Kutta Finite-Difference Schemes
    for the Nonlinear Schrödinger Equation.

    R.M. Caplan and R. Carretero-González.
    Applied Numerical Mathematics. 71 (2013) 24-40. PDF.
    Awarded the 6th most successful IMACS paper published in 2013 in Applied Numerical Mathematics.


  1. Existence, Stability, and Scattering of Bright Vortices in the
    Cubic-Quintic Nonlinear Schrödinger Equation.

    R.M. Caplan, R. Carretero-González, P.G. Kevrekidis, and B.A. Malomed.
    Mathematics and Computers in Simulation. 82,7 (2012) 1150-1171. PDF.


  1. Simulating the Nonlinear Schrödinger Equation using the Computational Capability of NVIDIA Graphics Cards
    R.M. Caplan and R. Carretero-González.
    ACSESS Proceedings. ACSESS 2010, (2010) AP10-04. PDF.


  1. Azimuthal Modulational Instability of Vortices in the
    Nonlinear Schrödinger Equation.

    R.M. Caplan, Q.E. Hoq, R. Carretero-González, and P.G. Kevrekidis.
    Optics Communications. 282,7 (2009) 1399-1405. PDF.
  2. Existence of Steady State Bright Vortex Solutions to the Cubic- Quintic Nonlinear Schrödinger Equation
    R.M. Caplan and R. Carretero-González.
    ACSESS Proceedings. ACSESS 2009, (2009) AP0903. PDF.

Other Works

  1. The Open Flux Problem: The Need for High Latitude Observations.
    J.A. Linker, P. Riley, C. Downs, R.M. Caplan, C. DeForest, S.E. Gibson, D.M. Hassler,
    J.T. Hoeksema, W.D. Pesnell, X. Sun, and N.M. Viall.
    Heliophysics 2024 Decadal Whitepapers. Bulletin of the AAS 55(3) (2023). PDF.
  2. From MPI to MPI+OpenACC: Conversion of a legacy FORTRAN
    PCG solver for the spherical Laplace equation.

    R. M. Caplan, Z. Mikic, and J. A. Linker.
    Presented at the 2017 NVIDIA GPU Technology Conference. arXiv:1709.01126 (2017) PDF.

Ph.D. Dissertation

Study of Vortex Ring Dynamics in the Nonlinear Schrödinger Equation utilizing
GPU-Accelerated High-Order Compact Numerical Integrators

Ph.D. Dissertation in Computational Science (2012).
Joint program with Claremont Graduate University and San Diego State University.
Committee Chair: Professor Ricardo Carretero.
Abstract▼. DOI: 10.5642/cguetd/52.

Masters Thesis

Azimuthal Modulational Instability of Vortex Solutions to the
Two Dimensional Nonlinear Schrödinger Equation

Masters Thesis in Computational Science (2008).
San Diego State University.
Thesis chair: Professor Ricardo Carretero.
Abstract▼ PDF.