Jakobus le Roux

Associate Professor

 

Office: Cramer Hall 2040

Phone: 256-961-7321

Email: jar0013@uah.edu

 

 

Education

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

 

Research interests

Field: Heliospheric space plasma physics - energetic charged particle behavior.

 

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.

 

Current Graduate Students

 

Aaron Arthur

Ph.D. expected 2015

Dissertation: "A focused transport model for solar energetic particle acceleration at fast traveling shocks driven by extreme coronal mass ejections".

Junye Ye

Ph.D. expected 2015

Dissertation: "A kinetic transport model for interstellar pickup ion acceleration at the heliospheric termination shock".

 

Past Graduate Students

 

Edmont Smith

M.S. 2010 (non-thesis)

 

Selected recent publications

  1. Alouani-Bibi, F., and le Roux, J. A., Transport of cosmic-ray protons in intermittent heliopsheric turbulence: Model and simulations, Astrophysical Journal, 781, 93 (2014).
  2. Florinski, V., Jokipii, J. R., le Roux, J. A., and Aloiani-Bibi, F., Energetic particle anisotropies at the heliospheric boundary, Astrophysical Journal Letters, 776, L37 (2013).
  3. Arthur, A. D., and le Roux, J. A., Particle acceleration at the heliospheric termination shock with a stochastic shock obliquity approach, Astrophysical Journall Letters, 772, L26 (2013).
  4. Shalchi, A., Dosch, A., le Roux, J. A., Webb, G. M., and Zank, G. P., Magnetic-field-line random walk in turbulence: A two-point correlation function description, Physical Review E, 85, 026411 (2012).
  5. le Roux, J. A., and Webb, G. M., A focused transport approach to the time-dependent shock acceleration of solar energetic particles at a fast traveling shock, Astrophysical Journal, 746, 104 (2012).
  6. le Roux, J. A., The effect of intermittent gyro-scale slab turbulence on parallel and perpendicular cosmic-ray transport, Astrophysical Journal, 743, 72 (2011).
  7. le Roux, J. A., Webb, G. M., Shalchi, A., and Zank, G. P., A generalized nonlinear guiding center theory for the collisionless anomalous perpendicular diffusion of cosmic rays, Astrophysical Journal, 716, 671 (2010).
  8. Shalchi, A., le Roux, J. A., Webb, G. M., and Zank, G. P., Analytical description for field-line wandering in strong magnetic turbulence, Physical Review E, 80, 066408 (2009).
  9. Florinski, V., Decker, R. B., le Roux, J. A., and Zank, G. P., An energetic-particle-mediated termination shock observed by Voyager 2, Geophysical Research Letters, 36, L12101 (2009).
  10. Shalchi, A., Webb, G. M., Le Roux, J. A., and Zank, G. P., Compound perpendicular transport of charged particles with drift, advection, wave propagation effects, and an arbitrary turbulence spectrum, Astrophysics and Space Science, 321, 197 (2009).
  11. le Roux, J. A., and Webb, G. M., Time-dependent acceleration of interstellar pickup ions at the heliospheric termination shock using a focused transport approach, Astrophysical Journal, 693, 534 (2009).
  12. Shalchi, A., le Roux, J. A., Webb, G. M., and Zank, G. P., Nonlinear field-line random walk for non-Gaussian statistics, Journal of Physics A, 42, 345501 (2009).

 

Recent grants and contracts

  1. The implication of non-Gaussian magnetic field-line wandering for the anomalous diffusion and shock acceleration of cosmic rays (NASA HSR) - $407,423.
  2. Anomalous diffusion in the collisionless solar wind plasma (NSF-DOE) - $438,228.
  3. Modeling the radial dependence of the shock acceleration of solar energetic particles from the corona to Earth with a time-dependent focused transport model (NASA LWS) - $439,902.
  4. Probing the physics of the heliopause region (NASA NNH13ZDA001N-HSR) - $396,020.