Energy and nuclear charge dependence of abundance enhancements of solar cosmic ray heavy ions in three large solar events

The differential flux and energy spectra of solar cosmic-ray heavy ions of He, C, O, Ne, Mg, Si, and Fe were determined in the energy interval E=3-30 MeV amu super(-) super(1) for two large solar events of Jan. 24, 1971, and Sept. 1, 1971, in rocket flights made from Ft. Churchill. From these data, the relative abundances and the abundance enhancement factors, xi , relative to photospheric abundances were obtained for these elements. Similar results were obtained for a third event on Aug. 4, 1972, from the available published data. Characteristic features of xi vs. nuclear charge dependences were deduced for five energy intervals. The energy dependence of xi for He shows a moderate change by a factor of similar to 3, whereas for Fe, xi shows a dramatic decrease by a factor of 10-20, with increasing energy. It is inferred that these abundance enhancements of solar cosmic-ray heavy ions at low energies seem to be related to their ionization states (Z*) and, thus, studies of Z* can give information on important parameters, such as temperature and density, in the accelerating region in the Sun.