Injection and Interplanetary Transport of Near‐Relativistic Electrons: Modeling the Impulsive Event on 2000 May 1

We present a Monte Carlo method to model the transport of solar near-relativistic electrons in the interplanetary medium, including adiabatic focusing, pitch-angle dependent scattering, and solar wind effects. By taking into account the angular response of the LEFS60 telescope of the EPAM instrument on board the ACE spacecraft, we transform the simulated pitch-angle distributions into the sectored intensities measured by the telescope. The goal is to deconvolve the effects of the interplanetary transport in order to infer the underlying injection profile and the radial mean free path of the electrons. We apply the model to the near-relativistic electron event observed on 2000 May 1, associated with an impulsive X-ray flare, type III radio bursts, and a narrow fast CME. The deconvolved interplanetary transport conditions reveal a long radial mean free path of 0.9 AU and pitch-angle dependent scattering. The eight observed sectored intensities are fitted in detail for more than 90 minutes, except for a short period (~12 minutes) right after the time of peak intensities. This discrepancy may suggest that the assumed scattering model performs more efficiently than the actual scattering processes at work. The resulting injection profile consists of two main components, an initial component lasting 2-3 minutes and probably related to a type III radio burst observed by WIND WAVES at ~10:21 UT, and a delayed component starting at the Sun around 10:35 UT with a typical injection decay timescale of ~0.5 hr. The delayed component may be related to the CME-driven shock.