HR: 13:40h
AN: SH33B-01    [Abstracts]
TI: Variability of the Nitrogen Abundance in the Solar Wind and Implications for Past Solar Activity
AU: * Wimmer-Schweingruber, R F
EM: wimmer@physik.uni-kiel.de
AF: Institut f\"ur Experimentelle und Angewandte Physik, Christian-Albrechts-Universit\"at zu Kiel,, Leibnizstr.\,11, Kiel,, Kiel, 24118 Germany
AU: Bochsler, P
EM: bochsler@soho.unibe.ch
AF: Physikalisches Institut, Universit\"at Bern, Sidlerstr.\,5, Bern, 3012 Switzerland
AU: Wurz, P
EM: wurz@soho.unibe.ch
AF: Physikalisches Institut, Universit\"at Bern, Sidlerstr.\,5, Bern, 3012 Switzerland
AU: Gloeckler, G
AF: University of Michigan, 2455 Hayward St., AOSS, Ann Arbor, MI 48109 United States
AU: Gloeckler, G
AF: Dept. of Physics, University of Maryland,, Space Physics,, College Park, MD 20742 United States
AU: Geiss, J
AF: International Space Science Institute, Hallerstr.\,6,, Bern, 3012 Switzerland
AU: Kallenbach, R
AF: International Space Science Institute, Hallerstr.\,6,, Bern, 3012 Switzerland
AU: Zurbuchen, T H
AF: University of Michigan, 2455 Hayward St., AOSS, Ann Arbor, MI 48109 United States
AB: The abundance of nitrogen in the heliosphere is an enigma. Laboratory analysis of lunar soils shows that trapped nitrogen is overabundant in them by about one order of magnitude relative to all noble gases, which in turn are efficiently trapped in the lunar regolith. On the other hand, the Solar Wind Ion Mass Spectrometer (SWIMS) on ACE has successfully measured the elemental abundance of nitrogen in the solar wind, N/O $ \approx0.121 \pm 0.014$, in good agreement with the photospheric value of N/O $\approx 0.123$ and with the SEP-dervied coronal value. In this work we determine the abundance ratio N/Ne and investigate the variability of N/O and of N/Ne in the solar wind. Nitrogen is not readily measured in the solar wind with spaceborn TOF mass/mass per charge spectrometers such as SWICS because it is not very abundant and is neighbored in mass and in mass per charge by the more abundant heavy ions, oxygen and carbon. For this reason, previous elemental abundance determinations of nitrogen in the solar wind have had large intrinsic uncertainties. However, with SWIMS, nitrogen is cleanly separated from its neighbors and its abundance can be accurately measured. Analyzing data from 1998 to 2004, we have found no unexpected variability of N in the solar wind, the ratios N/O and N/Ne are consistent with a constant value throughout this period of dramatically changing solar activity. We apply this finding to different ideas relating nitrogen in lunar soils to widely different solar input in the distant past and find that our result provides further evidence for a non-solar origin of most of nitrogen in lunar soils.
DE: 7500 SOLAR PHYSICS, ASTROPHYSICS, AND ASTRONOMY
DE: 5400 PLANETOLOGY: SOLID SURFACE PLANETS
DE: 6250 Moon (1221)
DE: 2100 INTERPLANETARY PHYSICS
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting