Solar wind carbon, nitrogen and oxygen abundances measured in the Earth's magnetosheath with AMPTE/CCE

Abstract

The solar wind number density ratios of C 6+ + C 5+ and N 7+ + N 6+ + N 5+ relative to O 8+ + O 7+ + O 6+ have been measured for the first time using data from the Charge‐Energy‐Mass (CHEM) Spectrometer on the AMPTE/CCE spacecraft during four solar active periods from Sept. 19 to Nov. 1, 1984 when CCE traversed the subsolar magnetosheath of the compressed magnetosphere. We find the average values of the density ratios of C/O and N/O to be 0.43±0.03 and 0.15±0.06, respectively. These ratios, as well as our average He 2+ /O ratio of 43±5 for these same time periods, are in excellent agreement with Solar Energetic Particles (SEP) abundance ratios as well as SEP‐derived coronal abundances of these elements. Our solar wind C/O ratio is substantially below the generally accepted photospheric value of 0.60.