1. High Latitude Oxygen LENA
Gordon R Wilson
Mission Research Corporation, Nashua NH
Thomas E. Moore and Michael Collier
Goddard Space Flight Center, Greenbelt MD

2. This is what we hoped to see.

3. This is what we saw.

4. LENA spin-time spectrogram for 24 August, 2000.

8. Integrated perigee pass signal intensities plotted (in
arbitrary units) versus time along with magnetic
activity as indicated by Ap.

9. Questions:
Why is the perigee signal (one of the
strongest seen by LENA) only visible near
perigee?
2. Why does the perigee pass signal have
such a broad distribution in spin angle?
3. Why does the overall intensity of the
Perigee pass signal not always track mag-
netic activity?

10. Oxygen Orbits Orbits of oxygen atoms launched from 1000 km11 9
7.5 6
4.5 3
Oxygen Orbits
Orbits of oxygen atoms launched from 1000 km
altitude and -65˚ magnetic latitude with the indicated
energies (eV).

15. Perigee and transverse distance to perigee for oxygen
atoms launched at 800 km altitude with the indicated
Launch angle (with respect to horizontal) and energy.

16. Perigee and transverse distance to perigee for oxygen
atoms launched at 1600 km altitude with the indicated
Launch angle (with respect to horizontal) and energy.

17. Differential scattering cross sections for atomic oxygen
on various gasses.

18. Conclusions:
The perigee pass signal consists primarily of
low energy (< 40 eV) oxygen atoms.
2. These atoms are energized in a low altitude
region (< 2000 km), very likely only in the
auroral zone.
3. There is a high energy ( eV) component
of thermospheric oxygen that consists of atoms
trapped in orbits around the earth.
4. LENA emitted from the auroral zone can
scatter out of the lower atmosphere in regions
distant from their point of origin contributing
to the diffuse appearance of the emissions.