Interim standard for the ion-neutral atomic oxygen collision frequency

A growing body of evidence based on radar and optical observations of winds in the Earth's upper atmosphere indicates that the commonly utilized value for the ion‐neutral atomic oxygen (O+‐O) collision frequency for momentum transfer is too low by a factor of 1.3–2. A revised standard for the O+‐O momentum transfer collision frequency is therefore recommended based on all the available measurements, in order to facilitate comparisons with thermospheric and ionospheric models and among data sets until future accurate laboratory measurements and more reliable observations can be made. The new interim standard, representing a 70% increase from the previous value, is given by: ν o+−o = 4×10−17 Tr0.5 no, where Tr = (Ti+Tn)/2, Ti being ion temperature, Tn neutral temperature, and no atomic oxygen number density in m−3.