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Calculated photoelectron pitch angle and energy spectraCalculations of the steady-state photoelectron energy and angular distribution in the altitude region between 120 and 1000 km are presented. The distribution is found to be isotropic at all altitudes below 250 km, while above this altitude anisotropies in both pitch angle and energy are found. The isotropy found in the angular distribution below 250 km implies that photoelectron transport below 250 km is insignificant, while the angular anisotropy found above this altitude implies a net photoelectron current in the upward direction. The energy anisotropy above 500 km arises from the selective backscattering of the low energy photoelectron population of the upward flux component by Coulomb collisions with the ambient ions. The total photoelectron flux attains its maximum value between about 40 and 70 km above the altitude at which the photoelectron production rate is maximum. The displacement of the maximum of the equilibrium flux is attributed to an increasing (with altitude) photoelectron lifetime. Photoelectrons at altitudes above that where the flux is maximum are on the average more energetic than those below that altitude.
Document ID
19740025751
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Mantas, G. P. (Illinois Univ. Urbana, IL, United States)
Bowhill, S. A. (Illinois Univ. Urbana, IL, United States)
Date Acquired
September 3, 2013
Publication Date
January 1, 1974
Subject Category
Geophysics
Report/Patent Number
NASA-CR-140040
Accession Number
74N33864
Funding Number(s)
CONTRACT_GRANT: NGR-07-004-109
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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