Complex sentence: This line results from the formation of deuterium via the union of a neutron and proton; in a solar flare the neutrons appear as secondaries from interactions of high-energy ions accelerated in the flare process.
Split into simpler sentences: This line results from the formation of deuterium via the union of a neutron and proton. In a solar flare the neutrons appear as secondaries from interactions of high-energy ions accelerated in the flare process.