Empirical determination of the o+o collision frequency

Details Empirical determination of the o+o collision frequency Empirical determination of the o+o collision frequency

Oct 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998jastp..60.1485o&link_type=abstract

Journal of Atmospheric and Solar-Terrestrial Physics, Volume 60, Issue 15, p. 1485-1496.

Physics

2

Scientific paper

The collision frequency between an oxygen atom and its singly charged ion controls the transfer of energy between the solar radiation and the thermosphere. We define a factor F, often called the Burnside factor, as the ratio of the empirical to the theoretical collision frequencies whose deviation from unity is a measure of inconsistency between theory and observation. Assuming given values for the theoretical parameters, here we apply the observational data to the empirical determination of this factor. The data are taken at the Millstone Hill Observatory, which consist of two distinct sets of data A and B.Three methods of analysis have been used. These are the method of linear-least-squares, a method due to [Hines et al., 1997], and a third method based on lognormal distribution of the data. While the linear-least-squares and lognormal distribution methods are based on Gaussian and lognormal distributions, respectively, no distribution assumption is made in the Hines et al. method, and this makes the method more general. The linear-least-squares and the Hines et al. methods give consistent estimates for F, differing in values from each other by only a few units in their third decimal places. Based on [Pesnell et al., 1993] calculated collision frequency, the F estimates for the sets A and B are 0.91 and 1.06, respectively.In addition, [Hines et al., 1997] and lognormal distribution methods set rigorous upper and lower bounds on the estimates of F. The bounds in the two methods are consistent with each other. Designating the true value of F by Ft, based on Pesnell et al. calculated collision frequency, we obtain 0.89 < Ft < 1.02, and 1.06 < Ft < 1.17 for the two sets A and B, respectively. Thus, the inequalities for the set A brackets the correct value of Ft = 1.0. We have also shown that the deviation of F for each measurement from Ft is lognormally distributed.It is shown that a shift of about 15% of the F estimates between the two sets indicated above is principally due to systematic errors in the oxygen atom densities in the two sets, which is of the order of 11%. An alternative way to find the atomic oxygen density by calculation is suggested here.To recommend a realistic formula for the user to calculate the collision frequency, without rigorous justification, we average the two estimates of F, leading to F¯ = 0.98. Since the [Pesnell et al., 1993] formula is valid to two significant figures, we recommend their formula with an uncertainty of 8% attached to it, which is due to the difference between the two estimates of F.

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