Carbon dioxide photoelectron energy peaks at Mars
Coates, A. J.; Kallio, E.; Fedorov, A.; Säles, T.; Schmidt, W.; Koskinen, H.; Riihelä, P.; Barabash, S.; Lundin, R.; Holmström, M.; Andersson, H.; Yamauchi, M.; Grigoriev, A.; Sauvaud, J. -A.; Thocaven, J. -J.; Winningham, J. D.; Frahm, R. A.; Sharber, J. R.; Scherrer, J. R.; Linder, D. R.; Kataria, D. O.; Luhmann, J. G.; Livi, S.; Curtis, C. C.; Hsieh, K. C.; Sandel, B. R.; Grande, M.; Carter, M.; McKenna-Lawler, S.; Orsini, S.; Cerulli-Irelli, R.; Maggi, M.; Wurz, P.; Bochsler, P.; Krupp, N.; Woch, J.; Fränz, M.; Asamura, K.; Dierker, C.; Roelof, E. C.; Kozyra, J. U.; Jeffers, S. J.; Williams, D. J.
United States, United Kingdom, Sweden, Finland, France, Ireland, Italy, Switzerland, Germany, Japan
Abstract
The ELectron Spectrometer (ELS) from the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) flown on the Mars Express spacecraft has an 8% energy resolution, combined with the capability to oversample the martian electron distribution. This makes possible the resolution and identification of electrons generated as a result of the He 304 Å ionization of CO 2 at the martian exobase on the dayside of the planet. Ionospheric photoelectrons were observed during almost every pass into the ionosphere and CO 2 photoelectron peaks were identified near the terminator. Atmospherically generated CO 2 photoelectrons are also observed at 10,000 km altitude in the martian tail near the inner magnetospheric boundary. Observations over a wide range of spacecraft orbits showed a consistent presence of photoelectrons at locations along the inner magnetospheric boundary and in the ionosphere, from an altitude of 250 to 10,000 km.