Solar energetic particles (SEPs) are one of the extreme space weather
phenomena. A huge SEP event increases the radiation dose received by aircrews,
who should be warned of such events as early as possible. We developed a
warning system for aviation exposure to SEPs. This article describes one
component of the system, which calculates the temporal evolution of the SEP
intensity and the spectrum immediately outside the terrestrial magnetosphere.
To achieve this, we performed numerical simulations of SEP transport in
interplanetary space, in which interplanetary SEP transport is described by the
focused transport equation. We developed a new simulation code to solve the
equation using a set of stochastic differential equations. In the code, the
focused transport equation is expressed in a magnetic field line coordinate
system, which is a non-orthogonal curvilinear coordinate system. An inverse
Gaussian distribution is employed as the injection profile of SEPs at an inner
boundary located near the Sun. We applied the simulation to observed SEP events
as a validation test. The results show that our simulation can closely
reproduce observational data for the temporal evolution of particle intensity.
By employing the code, we developed the WArning System for AVIation Exposure to
Solar energetic particles (WASAVIES).Comment: 23 pages, 11 figures, accepted for publication in Earth, Planets and
Spac