Comparison of the Prediction of HF Absorption during the March, 2012 PCA Event from Six Different Chemistry Schemes

The March, 2012 Polar Cap Absorption (PCA) event was well-captured by the network of Canadian NRCan riometers. This event, beginning March 7th, extended over a week, and corresponding bursts in proton fluxes
were observed at geostationary orbit by GOES detectors. In this poster, we compare the HF absorption predicted by six middle-atmosphere chemistry schemes: (1) a scheme developed at Los Alamos National Laboratory with 50+ species and over 1000 reactions, (2) the WACCM-D scheme, (iii) the University of Bern Atmospheric Ion Model (UBAIM), (iv) an older scheme developed by the Defense Threat Reduction Agency (DTRA), (v) a reduced scheme by Thomas & Bowman (1985), and (vi) a reduced scheme by Ozolin et al. (2009). Predictions of HF absorption from these six schemes are further contrasted with SWPC's operational D-Region Absorption Predictions (D-RAP) which assumes a square-root relationship between HF absorption (dB) and integral proton flux. This
case study provides an opportunity to determine the set of reactions and rates which distinguish our six schemes, and further assess how detailed chemistry modeling leads to absorption predictions that deviate from
D-RAP's assumed square-root phenomenology.