Diffusive-shock-accelerated interplanetary ions at several energies during the solar cycle 21 maximum

The most intense energetic particle (mainly proton) events in the energy range 36-1600 keV, during the years of maximum activity of solar cycle 21 (1978 to 1982), have been studied with regard to their spectra, temporal profiles. source location at the Sun, interplanetary plasma parameters and interplanetary magnetic field topology. In all the events, the particles were accelerated by the 'Diffusive Shock' acceleration mechanism, because all the events were 'long-duration events', shock-associated, and their spectra fitted to a power-law energetic particle spectrum dJ/dE similar to E-gamma with the exponent values ranging from 1.25 up to 1.94, with a mean value of 1.60 +/- 0.06. We also show that the spectral indexes gamma are related to the shock properties by a linear expression. The solar sources were located on a wide longitudinal belt extending from 500 W up to 73 degrees E. Neither the spectral indexes nor the shock parameters present any dependence on the source location at the Sun. Finally, only one event showed the complete set of properties that characterize the presence of a magnetic cloud associated with the event.