Passive Remote Sensing of Artificial Relativistic, Electron Beams iti the Middle Atmosphere

Two methods of passive remote sensing of mildly (E 5 MeV) relativistic electron beams as they prop-agate through the Earth’s upper and middle atmo-sphere are presented. Utilization of bremsstrahlung emissions as a diagnostic indicator of beam charac-teristic energy and particle flux is compared and con-trasted with that of the optical emission technique. A new MeV aurora1 electron model has been developed to compute line emission rates of O(lD)-+ O(3P) (X = 630.0-636.4 nm doublet), O(rS) + O(iD) (X = 557.7 nm), Nz(B3C,f) 3 N~(X2C~) (A = 391.4 nm and 427.8 nm from the N.$(lN) band), and Ns(C311,) 4 Nz(B3111,) (X = 337.1 nm from the Nz(2P) band). The 427.8 nm,.391.4 nm, and 337.1 nm lines are strong in intensity,.with production rates several or-ders of magnitude greater in than those of the 0 lines examined here. It is shown that the production of 337.1 nm is insensitive to compositional change and has a quenching height lower in altitude than the propagation depth of a 5 MeV electron beam, and thus the signature may be suitable as an indicator of electron flux for beams of comparable energy. The ratio of 427.8 nm to 391.4 nm emissions was found to be relatively ‘insensitive to compositional changes, and the ratio varies with altitude at lower altitudes, suggesting that it may suitable for inference of char-acteristic beam energy for MeV electron beams. Ad-vantages and disadvantages associated with both the bremsstrahlung and the optical techniques are pre-sented