In addition to the two ion species previously observed in the solar wind, ${}_{}{}^1{}_{}{}^{}\mathrm{H}_{}^{+}{}_{}{}^{}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}_{}^{++}{}_{}{}^{}$, Vela satellite measurements reveal the presence of ions of ${}_{}{}^3{}_{}{}^{}\mathrm{He}_{}^{++}{}_{}{}^{}$, ${}_{}{}^4{}_{}{}^{}\mathrm{He}_{}^{+}{}_{}{}^{}$, various ion species of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, and other unidentified heavy ions. From the number ratios of the ${\mathrm{O}}^{+7\mathrm{}}$, ${\mathrm{O}}^{+6\mathrm{}}$, and ${\mathrm{O}}^{+5\mathrm{}}$ ion species measured near earth, it may be inferred that the ionization state ratios are established deep within the solar corona at million-degree temperatures.

• Received 15 January 1968

DOI:https://doi.org/10.1103/PhysRevLett.20.393