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On Atmospheric Loss of Oxygen Ions from Earth Through Magnetospheric Processes
K. Seki,12*R.
C. Elphic,2M. Hirahara,3T. Terasawa,1T. Mukai4
In Earth's environment, the observed polar outflow rate for
O+ ions, the main source of oxygen above gravitational
escape energy,corresponds to the loss of ~18% of the present-day
atmosphericoxygen over 3 billion years. However, part of this apparent
losscan actually be returned to the atmosphere. Examining loss ratesof four escape routes with high-altitude spacecraft observations,we
show that the total oxygen loss rate inferred from currentknowledge is
about one order of magnitude smaller than the polarO+
outflow rate. This disagreement suggests that there may be asubstantial return flux from the magnetosphere to the low-latitudeionosphere. Then the net oxygen loss over 3 billion years dropsto
~2% of the current atmospheric oxygen content.
1 Department of Earth and Planetary Sciences,
University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113-0033, Japan.
2 NIS-1, MS D466, Los Alamos National Laboratory,
Los Alamos, NM 87545, USA.
3 Department of Physics,
Rikkyo University, Toshima, Tokyo 171-8501, Japan.
4 Institute of Space and Astronautical Science,
Sagamihara, Kanagawa 229-8510, Japan.
*
To whom correspondence should be addressed. E-mail:
seki{at}space.eps.s.u-tokyo.ac.jp
