Prof. David Ruffolo received his B.S. in Physics and B.A. in Mathematics from the University of Cincinnati, USA in 1985, at age 17.  He received his Ph.D. in Physics from the University of Chicago, USA in 1991, at age 23.  He initiated space physics research in Thailand, where he has worked for the past 26 years.  His awards include a 2014 Mahidol University Award for Research, a Senior Research Scholar Award from the Thailand Research Fund in 2016, and the 2017 Outstanding Scientist Award of Thailand.

Monte Carlo simulations of energetic particle transport in space, in Earth’s atmosphere, and in a cosmic ray detector

David Ruffolo

Department of Physics, Faculty of Science, Mahidol University, Bangkok, Thailand

 E-mail:; Fax: +66-2-354-7159; Tel. +66-2-201-5756



We present the results of Monte Carlo simulations to study cosmic rays, which are energetic particles from space.  To better understand cosmic ray transport in space, we have performed numerical experiments on the random walk of magnetic field lines (e.g., [1]) and energetic particles (e.g., [2]) in turbulent magnetic fields and complex distribution patterns of energetic particles from solar storms in interplanetary space, providing some predictions for the upcoming Parker Solar Probe mission to approach close to the Sun [3].  To interpret data from ground-based cosmic ray detectors, we have used the FLUKA program to model atmospheric showers of secondary particles due to cosmic ray interactions in Earth’s atmosphere, including estimates of atmospheric ionization and radiation doses of humans at aircraft altitude during a large solar storm [4].  We have also determined the sensitivity to secondary particles of the Princess Sirindhorn Neutron Monitor, a cosmic ray detector at Doi Inthanon, and can explain the absolute count rate to within 9% [5].  Furthermore, we also modeled the leader fraction (an indicator of the cosmic ray spectrum [6]) as measured by a neutron monitor on a ship during 2000-2006, and obtained very close agreement with the observed relative variation of the leader fraction [7].

Figure 1. Computing cluster at the Space Physics and Energetic Particles Laboratory, Department of Physics, Faculty of Science, Mahidol University


Keywords: Monte Carlo simulation, cosmic rays, energetic particle transport, radiation dosage.


  1. Sonsrettee, W., Subedi, P., Ruffolo, D., et al., J. Suppl., 2016, 225, 20.
  2. Ruffolo, D., Pianpanit, T., Matthaeus, W. H., and Chuychai, P., J. Lett., 2012, 747, L34.
  3. Tooprakai, P., Seripienlert, A., Ruffolo, D., Chuychai, P., and Matthaeus, W. H., J., 2016, 831, 195.
  4. Mitthumsiri, W., Seripienlert, A., Tortermpun, U., et al., Geophys. Res. Space Phys., 2017, 122, 7946.
  5. Mangeard, P.-S., Ruffolo, D., Sáiz, A., Madlee, S., and Nutaro, T., Geophys. Res. Space Phys., 2016, 121, 743.
  6. Ruffolo, D., Sáiz, A., Mangeard, P.-S., et al., J., 2016, 817, 38.
  7. Mangeard, P.-S., Ruffolo, D., Sáiz, A., et al., Geophys. Res. Space Phys., 2016, 121, 11620.