Central plasma sheet (CPS) ion conies are oxygen dominated with peak energies ranging from tens to hundreds of eV centered around pitch‐angles between 115 and 130 degrees. Because of the lack of correlation between the CPS conics and the observed currents and/or electron beam‐like structures, it is not likely that all of these conies are generated by interactions with electrostatic ion cyclotron waves or lower hybrid waves. Instead, we suggest that the observed intense broad band electric field fluctuations in the frequency range between zero and a hundred Hz can be responsible for the transverse energization of the ions through cyclotron resonance heating with the left‐hand polarized electromagnetic waves. This process is much more efficient for heating the oxygen ions than hydrogen ions, thus providing a plausible explanation of the oxygen dominance in CPS conies. Simple algebraic expressions are given from which estimates of conic energy and pitch angle can be easily calculated. This suggested mechanism can also provide some preheating of the oxygen ions in the boundary plasma sheet (BPS) where discrete aurorae form.

In the companion paper (Basu et al., this issue), a self-consistent transport-theoretic model for the combined electron-proton-hydrogen atom aurora was described. In this paper, numerical results based on the model are presented. This is done for the pure electron aurora, the pure proton-hydrogen atom aurora, and finally for the combined aurora. Adopting commonly used types of energy distributions for the incident particle (electron and proton) fluxes, we give numerical solutions for the precipitating electron, proton, and hydrogen atom differential number fluxes. Results are also given for ionization yields and emission yields of the following features: N• first negative group (3914 •), N 2 second positive group (3371 •), selected N 2 Lyman-Birge-Hopfield bands (1325 •, 1354 •, 1383 •, 1493 •, and all bands between 1700 and 1800 •), O I (1356 •), L• (1216 ]i), (4861 •), and H• (6563 •). The yield at 1493 • also contains a contribution from N I (1493 •), which in fact dominates LBH emission. A major new result of this study is that the secondary electron flux produced by the proton-hydrogen atom aurora is much softer than that produced by the electron aurora. This increased softness is due to the fact that (for energies of auroral interest) cross sections for secondary electron production by proton and hydrogen atom impact decrease exponentially with increasing secondary electron energy, whereas the cross sections for electron impact decrease as an inverse power law with increasing secondary energy. In our study of the pure electron aurora (no primary protons or hydrogen atoms present) and the pure protonhydrogen atom aurora (no primary electrons present), two important results obtain. First, certain emission features (for example, 3371 .&) are excited in completely different ways for the two kinds of aurora. Second, the "eV per electron-ion pair" as a function of the characteristic energy E 0 is nearly constant for the pure electron aurora, with a value of about 34, but varies by about 20% for the pure proton-hydrogen atom aurora. In our study of the combined electron-proton-hydrogen atom aurora, two additional results obtain. Since the proton-hydrogen atom contribution to the total incident energy flux in the midnight sector is, on the average, about 20 to 25% of that of the electrons, we find that when it is neglected, the ionization yield as well as the yields of many emission features will be underestimated, on the average, by about the same percentage. We also find that in the morning sector of the combined aurora, a double bump in the altitude profile of the E region electron density is possible for certain auroral conditions. INTRODUCTIONIn the companion paper [Basu et al., this issue], hereafter referred to as paper 1, we described a self-consistent transporttheoretic model for the combined electron-proton-hydrogen atom aurora. In this paper we present some numerical results based on this model. We do this for the pure electron aurora (section 2), the pure proton-hydrogen atom aurora (section 3), and fin...

In this paper we present nearly coincident Chatanika radar electron density measurements and NOAA 6 particle data for a continuous (diffuse) auroral E layer with a peak electron density of 1–2 × 105 cm−3 produced entirely by proton precipitation. The radar and particle data are analyzed using the Jasperse‐Basu transport theoretic method and the semiempirical, continuous slowing down method of Rees. Comparisons between the radar results for the electron density profile and the two theoretical results are given. We conclude that the transport theoretic method of Jasperse and Basu gives a more accurate result for the shape of the electron density profile and for the location of its peak than the semiempirical, continuous slowing down method of Rees. We also apply the transport theoretic method to derive a closed form expression for the energy deposition function and compare the transport theoretic energy deposition function with that used by Rees in order to explain the differences in the electron density profiles obtained by the two theoretical methods.

In this paper we examine the relationship among certain prominent auroral FUV emission features, the incident electron spectrum, and the model neutral atmosphere. Given the neutral atmosphere, we show that for simple models of the incident electron spectrum (Maxwellian and Gaussian in energy), satellite measurements of FUV emission features, in principle, determine the incident electron spectrum. We also discuss the relationship between the incident electron spectrum and the E region plasma density profile for the continuous (diffuse) aurora and for a stable arc.

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