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Photoelectrons in the ionosphere: Radar measurements and theoretical computations
Author(s) -
Cicerone Ralph J.
Publication year - 1974
Publication title -
reviews of geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 8.087
H-Index - 156
eISSN - 1944-9208
pISSN - 8755-1209
DOI - 10.1029/rg012i002p00259
Subject(s) - ionosphere , photoelectric effect , millstone hill , incoherent scatter , airglow , radar , physics , computational physics , f region , plasma , satellite , remote sensing , geophysics , atmospheric sciences , optics , astronomy , geology , computer science , telecommunications , quantum mechanics
Ionospheric photoelectrons may be studied by measuring the power returned in the plasma lines of the radar incoherent scatter spectrum. This paper reviews the type and quality of information about photoelectrons available from radar measurements. Distinctive capabilities and limitations of this ground‐based technique are discussed, and results are presented for a number of plasma line studies, mostly at Arecibo, Puerto Rico, and Millstone Hill, Massachusetts. These results are compared with measurements by satellite‐borne instruments and certain findings of theoretical studies of photoelectrons. It is noted that measured photoelectron escape fluxes generally exceed those predicted by current theories and that inadequate input data for theoretical computations are the likely cause of the discrepancy. Other outstanding problems involving photoelectrons require further research and are described here. One of these is the quantitative evaluation of photoelectron transport and energy degradation in the plasma contained in the magnetospheric field tubes. Experimental and theoretical work is needed on this problem to achieve quantitative understanding of protonospheric thermal structure and of predawn temperature and airglow enhancements in the F region of the ionosphere.