Solar near-relativistic electron observations as a proof of a back-scatter region beyond 1 AU during the 2000 February 18 event

Aims. We study the near-relativistic (NR; >30 keV) electron event observed on 2000 February 18 by near-Earth spacecraft. Previous works have explained this event by assuming that the propagation of NR electrons is essentially "scatter-free" at heliocentric radial distances r 0.5 AU) and anisotropic pitch-angle scattering for r < 1 AU, and a small radial mean free path (λ r < 0.5 AU) and isotropic scattering in the back-scatter region. Conclusions. The event cannot be explained without assuming a back-scatter region beyond 1 AU. The best fit is obtained by assuming λ r = 3.2 AU in the inner heliosphere and a back-scatter region characterized by a small mean free path λ r = 0.2 AU located beyond 1.2 AU.