  Conversion of electromagnetic energy into magnetohydrodynamic energy occurs
when the electric conductivity changes from negligible to finite values. This
process is relevant during the epoch of reheating of the early Universe at the
end of inflation and before the emergence of the radiation-dominated era. We
find that conversion into kinetic and thermal energies is primarily the result
of electric energy dissipation and that the magnetic energy plays only a
secondary role in this process. This means that, since electric energy
dominates over magnetic energy during inflation and reheating, significant
amounts of electric energy can be converted into magnetohydrodynamic energy
when conductivity emerges early enough, before the relevant length scales
become stable.
