Formation of the Injection Function of Solar Energetic Particles in Gradual Events

We present a model for solar energetic particle injection into interplanetary space in gradual events, in which particle acceleration occurs in a limited region of the solar atmosphere. The distribution function of particles accelerated by the diffusion mechanism is calculated. The flux of injected solar energetic particles is determined as a function of time and energy. We provide an explanation of the characteristic properties of the injection function and their dependence on the particle energy. Comparing the calculation results with ground-based measurements in the 2001 April 15 event shows a rough agreement with the particle density as a function of time and good agreement with the spectrum of maximum intensity values.