Atomic Oxygen Ion‐Neutral Collision Frequency Models at Ionospheric Temperatures

Abstract

The collision between atomic oxygen and its first positive ion plays a major role in Earth's F region ionosphere. An accurate corresponding collision frequency model is necessary to quantitatively understand the ionosphere. However, the widely used classic Banks theoretical model typically provides a collision frequency that is 30% lower than the expectation from ionospheric observations. Accordingly, the classic collision frequency is often adjusted by multiplying it by a constant known as the Burnside factor. This correction‐factor model adopted the classic model as its basis due to a misunderstanding that the classic model was based on a laboratory experiment; that is, the correction factor was originally meant to compensate for laboratory contamination. In this study, a collision frequency model is constructed based on the laboratory experiment, and the resultant laboratory‐based model is found to be consistent with ionospheric observations. In this construction, the impact of laboratory contamination is determined to be small (7%) and is mostly canceled by a misinterpretation regarding the conventional definitions of energy. Thus, the 30% difference is mainly caused by a theoretical error in the classic model itself. This error is energy‐dependent and corrected by the later wide‐energy theoretical model. Thus, the classic model cannot be corrected by a temperature‐independent constant and should be replaced by the later model.

Estimation of Ion Temperature in the Upper Ionosphere Along the Swarm Satellite Orbits

“…Note that the O + -O collision cross section has usually been associated with large uncertainties (e.g., Salah, 1993). Recent analysis by Ieda (2021) indicated, however, that the cross section in the ionospheric energy range and based on a wide-energy theory type model (e.g., Stallcop et al, 1991) is more accurate than those based on classical models and their temperature-independent corrections. The collision frequency given by Pesnell et al (1993) represents a refined version of that given by Stallcop et al (1991), and agrees very well with it, but avoids use of a tabulated form of collision integrals.…”

Curved Trajectory Effect on Charge‐Exchange Collision at Ionospheric Temperatures

“…This model is based on Stebbings et al (1964), who conducted an ion-beam experiment to measure the energy-dependent CXCS of O + -O collision at 40-10,000 eV. Their experiment was contaminated with excited-state O + , and their results were adjusted by Ieda (2021) to the ground-state O + -only case. The resultant model is characterized by charge-exchange constants ) which are defined in Equation A1.…”

“…We use the O + -O charge-exchange collision model proposed by Ieda (2021). This model is based on Stebbings et al (1964), who conducted an ion-beam experiment to measure the energy-dependent CXCS of O + -O collision at 40-10,000 eV.…”

“…a This energy is the conventional kinetic energy used in theoretical atomic collision studies, also known as the kinetic energy of relative motion or the kinetic energy of the reduced mass particle. See further explanations in Appendix A of Ieda (2021). b This is also known as the average diffusion or momentum-transfer cross section Ǭ D in Banks (1966) and Banks and Kockarts (1973), which is the same as the collision integral Ω 1,1 (T) in Pesnell et al (1993) and Hickman et al (1997).…”