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Apollo ALSEP/SIDE Observations of Stairstep Flux Profiles in the Terrestrial Magnetotail

Anastasia Newheart
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Abstract Text: 

We present Apollo 14 Suprathermal Ion Detector Experiment (SIDE) observations of unusual stairstep flux spectra observed on the lunar dayside surface while the moon was in the magnetotail. These stairstep flux spectra exhibit an approximately constant flux, usually between 100 and 1000 Hz/(eV cm^2), at low energies and then drop off dramatically, usually by over an order of magnitude, at some cut-off energy with flux in the highest energy channels between 1 and 10 Hz/(eV cm^2).
We found 27 time periods exhibiting these stairstep flux profiles between November 1971 and June 1972. 20 of these spectra had a cutoff energy of 100eV, 4 had a cutoff energy of 250eV, 2 had a cutoff energy of 30eV and for one it was 17eV. By examing the Dst and Kp indexes, there appears to a correlation between the occurrence frequency of these spectra and the level of geomagnetic activity. We discuss a possible interpretation of these events as resulting from non-montononic potentials on the lunar surface which have been observed by the Lunar Prospector Electron Reflectometer as well as by the ARTEMIS spacecraft.

T. K. Greathouse K, D. Rutherford, K. E. Mandt, D. M. Hurley, J. T. S. Cahill, G. R. Gladstone, D. E. Kaufmann
SSERVI Identifier: 

Recognizing that science and human exploration are mutually enabling, NASA created the Solar System Exploration Research Virtual Institute (SSERVI) to address basic and applied scientific questions fundamental to understanding the Moon, Near Earth Asteroids, the Martian moons Phobos and Deimos, and the near space environments of these target bodies. As a virtual institute, SSERVI funds investigators at a broad range of domestic institutions, bringing them together along with international partners via virtual technology to enable new scientific efforts."