Observations related to the acceleration, injection, and interplanetary propagation of energetic protons during the solar cosmic ray event on February 16, 1984

Data from the worldwide network of neutron monitors and from the cosmic ray telescopes on IMP 8 have been used to deduce the intensity‐time profiles, the anisotropy‐time profiles, the energy spectra, and the pitch angle distributions of the solar protons near Earth during the solar cosmic ray event on February 16, 1984. In addition, measurements by particle detectors on the GOES 5 and 6 and ICE spacecraft were used in the analysis. The pronounced anisotropy of the particle fluxes, lasting ∼40 min at relativistic energies and more than 2 hours at ∼75 MeV, shows that the propagation of the solar protons in the interplanetary magnetic field (IMF) was practically scatter‐free (mean free path λ ≳ 2 AU) and that the injection of the particles into the IMF at the Sun was time‐extended. Although the analysis of the onset times of the event as a function of the reciprocal of the proton speeds does not clearly exclude a δ‐like acceleration of the flare protons, we infer that the solar protons with 70‐ to 500‐MeV energy were injected into the IMF 4 ± 2 min earlier than the relativistic protons. Proton energy spectra at the Sun over a range from 25 MeV to 10 GeV, as constructed from the solar proton observations at Earth, evolved with time in both amplitude and energy. The time evolution of the energy spectra at the Sun also suggests that the lower‐energy protons were accelerated earliest. These observations are consistent with an acceleration of the protons by a coronal shock.