Mid-LatitudeERegion: An Examination of the Existence of a Corpuscular Source

Abstract

We present new data from two rocket flights and examine the published evidence for the existence of a corpuscular source of ionization at E region heights. The rockets were launched from White Sands Missile Range (magnetic latitude of ∼43°) to provide measurements of energetic electrons and protons between 40 eV and 5.5 keV in the E region below 120 km. A daytime flight (solar zenith angle χ of 58°) launched during a geomagnetically disturbed period (Kp = 5‐) provided measurements of a small flux of electrons which exhibits a strong altitude dependence below 500 eV but essentially none above that energy. The observed electron energy flux at 116 km is ∼ 1.8 × 10−3 erg/cm² s. We interpret these to be photoelectrons. During the nighttime flight we observed an energy flux which was less than 10−5 erg/cm² s. Upper limits for proton fluxes are given. The electron flux values contrast sharply with much higher values reported by some other investigators. The implications of and some possible reasons for the differences are discussed. After reviewing our data and the relevant literature we conclude that (1) data obtained from one location must be carefully interpreted with regard to implications about the general ionosphere, since a real geographic variability exists; (2) since we observe no significant fluxes of energetic particles in a geomagnetically disturbed ionosphere, even in the presence of fluctuating nighttime E region ionization, the presence of such fluctuations cannot be taken as evidence of precipitating particles; and (3) many reports of corpuscular radiation contain high flux values which are not supported by observations of 391.4‐nm radiation from N2+.

VLF transmission induced slot electron precipitation

“…If high powered VLF transmitters routinely precipitate electrons, and it appears that they do, they may be responsible for the discrepancy in electron density in the iono-• sphere as measured by various investigators (see Morse and Rice, 1976 It is also possible that the energy input into the upper atmosphere in the vicinity of • such transmitters has a measureable effect on the weather. Bremsstrahlung produced at 80-100 km heights could penetrate to the lower atmosphere and produce ions which then • act as nucleation centers for water droplets.…”

An equilibrium model of plasmaspheric composition and density

“…In the past, there seemed to be little need for a comprehensive plasmaspheric model except possibly in the study of VLF and ULF characteristics (see, for example, Carpenter and Smith [1964], Fukunishi and Lanzerotti [1974a, b]). However, as the usage of VLF and ULF for communication purposes becomes more common [Koons, 1977], and as anthropogenic VLF noise increases [Helliwell et al, 1975], there is strong evidence that the radiation belt environment [Vampola, 1977] as well as the ionosphere [Morse and Rice, 1976] may be modified by these emissions. Since the controlled transmission of VLF communication signals and the environmental impact assessment of VLF noise upon the ionosphere and magnetosphere both require comprehensive models of plasmaspheric density and composition, a physical model of the plasmasphere may perhaps be a primary requirement for such applications.…”

Production of the low‐latitude night E layer

“…A review by Paulikas [1975] concluded that there could be significant E region production under some conditions. Morse and Rice [1976] examined the possibility of a corpuscular source for the night E region; they concluded that this was not needed, and a sufficient flux of energetic particles did not generally occur. Bauske et al [ 1997] The present paper was prompted by the recent publication of some good, mean data on electron densities in the lowlatitude night E region.…”