Dayside Magnetospheric Cleft Auroral Processes.

The present study details the analysis of measurements of the atomic oxygen (('3)P-('1)D) 6300 (ANGSTROM), (('1)D -('1)S) 5577 (ANGSTROM), atomic nitrogen (('4)S-('2)D) 5200 (ANGSTROM), and N(,2)('+) First Negative (0,1) 4278 (ANGSTROM) band emission features obtained from the launch of the Black Brant rocket AMF-VB-41 through the dayside magnetospheric cleft at 23:32:06 UT, December 6, 1974 from Cape Parry, NWT, Canada. Preliminary results have been presented by Shepherd et al. (1976b). A remarkable aspect of the optical measurements, obtained over a relatively large horizontal extent, is that the 5577 (ANGSTROM) and 4278 (ANGSTROM) emission shows a clearly defined decrease in intensity at the poleward boundary of the dayside particle precipitation, while the 5200 (ANGSTROM) emission continues well into the polar cap with no notable intensity decrease. The 6300 (ANGSTROM) emission displays a behaviour intermediate between these extremes. A dynamical model of dayside cleft auroral processes, including soft electron-ionosphere interactions and dayside auroral chemistry, has been developed and applied to the analysis of the AMF-VB-41 optical data. It is demonstrated that rocket-borne optical measurements may be used to infer the neutral and ion wind components along the rocket trajectory and, hence, delineate the effects of high-latitude ionospheric dynamics on the horizontal distribution of the dayside auroral emission features.