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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We demonstrate that cyclotron resonance with observed electric field fluctuations is responsible for production of the oxygen-ion conies that are observed by the Dynamics Explorer 1 satellite in the central plasma-sheet region of the Earth's magnetosphere. The ion-velocity distribution is described by a quasilinear diffusion equation which is solved by the Monte Carlo technique. The acceleration produced by the observed wave spectrum agrees well with the ion observations, in both form and magnitude. To our knowledge, this represents the first successful comparison of an observed conic with any theoretical model. 52.50.Gj, 52.65.+Z, 94.20.Rr Ion acceleration through wave-particle interaction with plasma turbulence in the auroral regions of the Earth's magnetosphere has commonly been invoked 1 to explain the origin of observed 2 intense fluxes of energetic ions flowing out of the ionosphere into the outer magnetosphere, which are known as "ion conies" because of the form of the ion distribution in velocity space. Until recently, 3 however, attempts to verify the theories by correlating ion-flux and plasma-turbulence data have been unsuccessful 4 : Because of the small spatial scale of energetic conies and the regions in which they form, it has proven difficult to observe simultaneously both an ion conic and the waves which are responsible for its generation. By the examination of a special class of conic events, namely, the oxygen-dominated, less-energetic conies produced in the broad central plasma-sheet (CPS) region of the auroral zone, we are able to report here the first successful description of an observed ion conic by a theoretical model of ion acceleration through waveparticle interaction. The theoretical ion-velocity distribution is calculated with use of a Monte Carlo technique which allows us to compare not only the overall magnitude of the acceleration produced by the observed turbulence, but also to compare the form of the ion-velocity distribution produced by the wave-particle interaction combined with the effect of the static, but inhomogenei ous, geomagnetic field.Such comparisons can be realized only where it is possible to measure the plasma turbulence and ion fluxes simultaneously.Intense, broad-band, low-frequency, electric and magnetic field noise has been commonly observed at low altitudes over the Earth's auroral zone by nearly all the satellites that have flown in this region. 5 Particle measurements 6 performed on board the Dynamics Explorer 1 (DE-1) satellite have revealed the existence of a population of oxygen-dominated ion conies that extend in latitude throughout the equatorward portion of the auroral zone (which maps out to the CPS in the Earth's magnetotail) during times of magnetic storm activity. These energetic particle fluxes are coincident with intense, low-frequency auroral-zone turbulence, 7 and it has been suggested 8 that wave-particle interaction with this turbulence is responsible for the transverse acceleration of the ions to form the observed conies. Based on the lab...

The first self-consistent transport-theoretic model for the combined electron-proton-hydrogen atom aurora is presented. This is needed for accurate modeling of the diffuse aurora, particularly in the midnight sector, for which a statistical study (Hardy et al., 1989) indicates that the proton contribution to the total auroral energy flux is (on the average) about 20 to 25% of that of the electrons. As a result, the ionization yield as well as the yields of many emission features will be underestimated (on the average) by about the same percentage if the proton-hydrogen atom contributions are neglected. The model presented here can also be used to study a pure electron aurora or a pure proton-hydrogen atom aurora by choosing the appropriate boundary conditions, namely, by setting the incident flux of one or the other particle population equal to zero. In the latter case, the new feature of the present model is the rigorous transport-theoretic treatment of the contributions to ionization rates and to emission rates and yields from the secondary electrons produced by protons and hydrogen atoms. A coupled set of three linear transport equations is presented. Protons and hydrogen atoms are coupled only to each other through charge-changing (charge exchange and stripping) collisions, while the electrons are coupled to both protons and hydrogen atoms through the secondary electrons that they produce. Source functions for the secondary electrons produced by the three primary particle populations are compared and contrasted, and the numerical methods for solving the coupled transport equations are described. Finally, formulas for calculating pertinent aurora-related quantities from the particle fluxes are given. In the companion paper (Strickland et al., this issue), the model results are presented. Jones, 1969; Chubb and Hicks, 1970; Rees and Benedict, 1970; Yevlashin, 1970; Eather and Mende, 1971]. It now appears that the disagreement was largely due to the difference between the statistical oval and the instantaneous oval [Vallance Jones, 1974]. With the advent of more or less continuous, satellite-based observations of the precipitating particles themselves, a clearer picture of the statistical distribution of the two ovals has emerged. Sharber [1981] used data from the soft-particle spectrometer on the ISIS 2 satellite to demonstrate that the maximum ion flux generally lies equatorward of the maximum electron flux, so that in the vicinity of the ion peak, the ion energy can provide a significant fraction of the total energy deposition. Since November 1982, satellites of the Defense Meteorological Satellite Program have carried SSJ/4 detectors that simultaneously measure the precipitating flux of ions and electrons [Hardy et al., 1989]. Prior to that date, only electron fluxes were measured. On the basis of earlier electron data, Hardy et al. [1985] produced a statistical model of auroral electron precipitation and, later, a functional representation of that model [Hardy et al., •1987]. On the basis of later ion data,...

In this paper we show that linear transport theory may be used to solve for the auroral proton and H atom fluxes in plane‐parallel geometry in the forward scattering and average discrete energy loss approximations. In this approximation, inelastic scattering is taken into account, but elastic scattering drops out and the solutions are approximations to the fluxes in the downward hemisphere. Using the multiple scattering method, we obtain the particle fluxes as finite sums of analytic functions of altitude, energy, and pitch angle. Closed form expressions are also found for the hemispherically averaged fluxes and the energy deposition and ionization rates. The notion of pseudoparticles is discussed and used to approximate the sums that occur in the above formulae. Results are presented for incident isotropic‐Maxwellian proton fluxes.