The positive ion‐molecule reactions N++O2→ NO++O→ O2++N, N2++O2→ O2++N2, O++O2→ O2++O, O++N2→ NO++N, were measured in a newly constructed flow‐drift tube apparatus. Reactions (a), (b), and (c) were measured from thermal energy to approximately 2 eV ion kinetic energy in the center of mass. Reaction (d) was measured from 0.3–3 eV ion kinetic energy. The data agree well with previous thermal values at low energies and agree well with beam data at the highest energy. In the case of all the reaction except (a), there is an initial decrease of the rate constant with increasing energy followed by an increase.

Flow‐drift technique for ion mobility and ion‐molecule reaction rate constant measurements. II. Positive ion reactions of N+, O+, and H2+ with O2 and O+ with N2 from thermal to [inverted lazy s]2 eV

We have obtained solutions of the coupled continuity, momentum, and energy equations for NO(+), O(+), and O2(+) ions for conditions appropriate to the daytime high-latitude E and F regions. Owing to the rapid increase of the reaction O(+) + N2 yielding NO(+) + N with ion energy, high-latitude electric fields and consequent perpendicular-E x B drifts deplete O(+) in favor of NO(+). For electric field strengths less than about 10 mV/m the depletion of O(+) is small, and the altitude profiles of ion density are similar to those found at mid-latitudes. However, for moderate electric field strengths (50 mV/m), NO(+) is substantially increased in relation to O(+) and becomes an important ion throughout the F region. For large electric fields (200 mV/m), NO(+) completely dominates the ion composition to at least 600 km, decreasing at high altitudes with a diffusive equilibrium scale height. Since the overall F region electron density decreases markedly with increasing electric field strength, it appears that high-latitude, daytime electron density troughs are directly related to the presence of ionospheric electric fields.

Effect of electric fields on the daytime high-latitude E and F regions

Energetic neutral atom (ENA) detectors have been successfully flown on missions such as the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) and are now an important tool for probing the geospace environment. Interpretation of ENA data, however, requires knowledge of a number of key charge transfer cross sections. Here we present a critical review of the published experimental measurements and recommend a set of parameterized cross sections. The processes considered are charge transfer of H + and O + with H, O, N 2 , and O 2 for collision energies from 10 eV to 100 keV. The limitations of the measurement techniques and the probable reliability of the recommended cross sections are addressed.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2005JA011298

Charge transfer cross sections for energetic neutral atom data analysis

A time-dependent three-dimensional model of the middle and high latitude ionosphere is described. The density distributions of six ion species (NO+ , O 2 + , N 2 + , O+ , N+ , He+) and the electron and ion temperatures are obtained from a numerical solution of the appropriate continuity, momentum and energy equations. The equations are solved as a function of height for an inclined magnetic field at E and F region altitudes. The three-dimensional nature of the model is obtained by following flux tubes of plasma as they convect or corotate through a moving neutral atmosphere. The model takes account of field-aligned diffusion, cross-field electrodynamic drifts, thermospheric winds, polar wind escape, energy-dependent chemical reactions, neutral composition changes, ion production due to solar EUV radiation and auroral precipitation, thermal conduction, diffusion-thermal heat flow and local heating and cooling processes. The model also takes account of the offset between the geomagnetic and geographic poles. A complete description of the ionospheric model is given, including a derivation of the relevant transport equations, formulas for all of the chemical and physical processes contained in the model, a discussion of the numerical technique, and a description of the required model inputs. The effects that various chemical and physical processes have on the ionosphere are also illustrated.

A mathematical model of the middle and high latitude ionosphere

The effects of non‐Maxwellian ion speed distributions on ion–neutral reaction rate constants measured in drift tubes are examined experimentally and are compared to the predictions of recent theories. The rate constants of strongly kinetic‐energy‐dependent ion–molecule reactions of O+ with O2, N2, and NO are measured separately in helium and argon buffer gases, in which the O+ speed distributions are expected to be very different. The differences between the helium‐buffered and argon‐buffered rate constants are often substantial. When different, the argon‐buffered values are generally larger than the helium‐buffered values at the same mean energy, indicating that the O+‐in‐argon distribution has a larger high‐energy ’’tail’’ than the O+‐in‐helium distribution. The differences between the two sets of data are compared to predictions from (a) the Monte Carlo trajectory calculations of Lin and Bardsley, and (b) the moment solution of the Boltzmann equation of Viehland and Mason, both described in accompanyin...

Effects of ion speed distributions in flow‐drift tube studies of ion–neutral reactions

Laboratory measurements indicate that the metastable ions of O+ in reaction with N2 in the low‐energy range (14 eV) react to form principally N2+, while the ion—molecule reaction to form NO+ has a very small probability. The ground‐state O+ ion reacts mainly to form NO+. The abundance of metastable O+ 2D ions was determined using the observation that O+(2D)+N2 has a small cross section for forming NO+. The ion energy dependence for both reactions has been measured within the energy range 1.0–500 eV.

D. A. Vroom

Papers

Effect of Metastable O+(2D) on Reactions of O+ with Nitrogen Molecules