bi-directional field-aligned

Yue, C., Bortnik, J., Thorne, R., Ma, Q., An, X., Chappell, C., et al. (2017). The characteristic pitch angle distributions of 1 eV to 600 keV protons near the equator based on Van Allen Probes observations. Journal Of Geophysical Research: Space Physics. http://doi.org/10.1002/2017JA024421 (Original work published August 2017)