Dr. Jakobus le Roux

Associate Professor, Space Science Department


Basic interests: Basic kinetic transport theory of energetic charged particles in tenuous nonuniform high-conductivity collisionless plasma flows, Quasi-linear, and nonlinear kinetic theory of energetic charged particle scattering and stochastic acceleration in turbulent low-frequency electromagnetic fields of tenuous collisionless high conductivity plasmas, Kinetic theory of energetic charged particle acceleration at collisionless shocks, Magnetohydromagnetic theory of large-scale plasma flow, Magnetohydromagnetic turbulence and weak turbulence kinetic theory.

Specific interests: All aspects of suprathermal (energetic) charged particle transport and acceleration in the solar wind plasma. Particle populations of interest include solar energetic particles, pickup ions, anomalous cosmic rays and galactic cosmic rays, Test particle and self-consistent finite difference and finite volume simulations of suprathermal charged particle transport and acceleration in the solar wind plasma, The acceleration of solar energetic particles at fast coronal mass ejection driven traveling bow shocks, including self-consistent wave generation, The acceleration of interstellar pickup ions at the heliospheric termination shock, including modification of the shock structure by the accelerated pickup ions (see figure), The acceleration of superthermal particles in a “sea” of contracting and merging (reconnecting) small-scale magnetic flux ropes in the supersonic solar wind plasma and in the corona, The non-diffusive parallel and perpendicular transport of energetic charged particles in intermittent low-frequency solar wind magnetic field turbulence including propagation of anomalous and galactic cosmic rays through the heliopause.

 spectra kobus

Comparison of Voyager 2 energetic ion spectral data behind the heliospheric termination shock as adapted from Decker et al., 2008 (left panel) with a kinetic focused transport theory simulation (right panel) of the shock accelerated interstellar pickup proton spectrum (left panel). The simulation illustrates the importance of including perpendicular diffusion of accelerated pickup ions across the termination shock due to magnetic field-line random walk in the shock acceleration process. The work was published in Astrophysical Journal Letters in 2013 with current Ph.D. student Aaron Arthur as the lead author.

Dr. Jakobus le Roux's Curriculum Vitae


  • Ph.D., Northwest University, South Africa, 1990
  • M.S., Northwest University, South Africa, 1987
  • B.S., University of Stellenbosch, South Africa, 1982

Classes Taught

Recent Grants & Contracts

  • Particle Acceleration in Inner Heliospheric Regions with Multiple Contracting and Reconnecting Magnetic Islands (NASA HSR) - $438,229
  • Probing the Physics of the Heliopause Region (NASA HSR) - $395,000

Selected Publications

  • le Roux, J. A., Webb, G. M., Khabarova, O. V., Zhao, L. L., & Adhikari, L., Modeling Energetic Particle Acceleration and Transport in a Solar Wind Region with Contracting and Reconnecting Small-scale Flux Ropes at Earth Orbit, The Astrophysical Journal, 887, 77, 2019. 25 pp.
  • Strauss, R. D., & le Roux, J. A., Solar Energetic Particle Propagation in Wave Turbulence and the Possibility of Wave Generation. The Astrophysical Journal, 872, 125, 2019. 15 pp.
  • le Roux, J. A., Zank, G. P. & Khabarova, O. V., Self-consistent Energetic Particle Acceleration by Contracting and Reconnecting Small-scale Flux Ropes: The Governing Equations, The Astrophysical Journal, 864, 158, 2018. 51 pp.
  • le Roux, J. A., Zank, G. P., Webb, G. M., & Khabarova, O. V., Combining Diffusive Shock Acceleration with Acceleration by Contracting and Reconnecting Small-scale Flux Ropes at Heliospheric Shock. The Astrophysical Journal, 827,47, 2016. 28 pp.
  • Ye, J., le Roux, J. A., & Arthur, A. D., Interstellar Pickup Ion Acceleration in the Turbulent Magnetic Field at the Solar Wind Termination Shock Using a Focused Transport Approach, The Astrophysical Journal, 826:117, 2016. 17 pp.
  • Strauss, R. D., le Roux, J. A., Engelbrecht, N. E., Ruffolo, D., & Dunzlaff, P., on-Axisymmetric Perpendicular Diffusion of Charged Particles and their Transport Across Tangential Magnetic Discontinuities, The Astrophysical Journal, 825, 43, 2016. 14 pp.
  • Alouani-Bibi, F., & le Roux, J. A., Transport of Cosmic-ray Protons in Intermittent Heliospheric Turbulence: Model and simulations, The Astrophysical Journal, 781, 93, 2014. 12 pp.
  • Arthur, A. D., & le Roux, J. A., Particle Acceleration at the Heliospheric Termination Shock with a Stochastic Shock Obliquity Approach, Astrophysical Letters, 772, L26, 2013. 5 pp.
  • le Roux, J. A. & Webb, G. M. A Focused Transport Approach to Time-dependent Shock Acceleration of Solar Energetic Particles at a Fast Traveling Shock, The Astrophysical Journal, 746, 104, 2012. 21 p
  • le Roux, J. A., The Effect of Intermittent Gyro-scale Slab Turbulence on Parallel and Perpendicular Cosmic-ray Transport, The Astrophysical Journal, 743, 72, 2011. 11 pp.
  • le Roux, J. A., Webb, G. M., Shalchi, A., & Zank, G. P., A Generalized Nonlinear Guiding Center Theory for the Collisionless Anomalous Perpendicular Diffusion of Cosmic Rays, The Astrophysical Journal, 716, 671, 2012.
  • le Roux, J. A. & Webb. G. M., Nonlinear cosmic-ray diffusive transport in combined 2D and slab MHD turbulence: A BGK-Boltzmann approach, The Astrophysical Journal, 667, 930, 2007.