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.

The solar flare of August 18, 1979: Incoherent scatter radar data and photochemical model comparisons

“…Before the flare, essentially all the positive ions at 80 km were polyatomic, consisting mainly of hydrated HaO + complexes, with recombination rate coefficients close to 3 X 10~6cm 3 /s. Determinations of <*<.// in the midlatitude D-region under moderately disturbed conditions have been reported by Larsen et al, 1976. Below 80-km altitude their values of a e jj are substantially larger than our values in Table II.…”

Electron loss rates from the outer radiation belt caused by the filling of the outer plasmasphere: The calm before the storm

“…Precipitating electrons with energies of 150 keV and above deposit most of their energy at altitudes of about 75 km and lower [e.g., Rees , 1963, 1964]. The effects of energetic electrons on atmospheric chemistry [e.g., Thorne , 1997; Callis et al , 1991, 1998; Rozanov et al , 2005; Randall et al , 2007], ionospheric profiles [e.g., Larsen et al , 1976; Goldberg et al , 1984; Frahm et al , 1997; Rodger et al , 2007], atmospheric electricity [e.g., Sheldon et al , 1988; Tinsley et al , 2007], and climate [e.g., Lastovicka , 1996; Kniveton and Tinsley , 2004] are presently being considered. Calms before storms precondition the magnetosphere for the storms in several ways [cf.…”

L-dependent energetic electron precipitation and mid-latitudeDregion ion pair production profiles

“…In an extensive study, Larsen et al [1976] have discussed simultaneous measurements of electron precipitation and D region electron density over Ottawa. The data analysis used here is similar to t•hat applied in the above study, as is the method for calculating the ion pair production rates from precipitating electrons [see Walt et al, 1968].…”