A coordinated study of energetic electron precipitation andDregion electron concentrations over Ottawa during disturbed conditions

Abstract

This article presents the results of a study of the energetic electron precipitation as well as important parameters of the D region over Ottawa (45°N, 76°W) during lightly to moderately disturbed conditions, using data for the period following the December 17, 1971, magnetic storm as well as data obtained on other selected days exhibiting anomalous D region absorption. Following the December 17, 1971, storm, significant fluxes of precipitating electrons of > 130 keV were observed near Ottawa, even during the poststorm period on December 20, when the geomagnetic activity had subsided (∑ Kp = 6). The excess ionization detected at D region altitudes above Ottawa can be explained as being due to ionization from a prolonged electron drizzle from the outer radiation belt. For the first time it has been proven that precipitating electrons from the radiation belt were the main cause of D region poststorm conditions of middle latitudes. The ground-based radio probing measurements of the free electron concentration have been coordinated with simultaneous satellite observations of the quasi-trapped and precipitating electron environment above the site. From the ground-based measurements, by using the partial reflection technique at two frequencies (2.66 and 6.275 MHz), electron concentration profiles for altitudes between ≈ 60 and 90 km have been derived at times when the low-altitude polar-orbiting satellite 1971-089A passed near Ottawa. On board this satellite, electron differential fluxes in 260 channels and at two pitch angles were measured at energies between ≈1 and ≈2800 keV. The ion pair production rate height profiles due to precipitating electrons were computed for D region heights by using nonisotropic energy-dependent pitch angle distributions. Effective electron loss rates were deduced for heights between 63 and 91 km. These results indicate a significant variability in loss rates in the altitude range 75–85 km.