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A newer empirical model of EM input has been developed by Cosgrove et al. (2014) (hereafter referred to as Cosgrove14) based on data from the FAST satellite. At the outset, the paper states that one goal of the model is to provide the high‐latitude electric field driver for GCMs. A major difference between the Weimer and Cosgrove models lies in the way Poynting flux is calculated. In W05, the EM energy is estimated from the average electric field <E> and the average magnetic perturbation <δB> as S = <E> x <δB > /μ₀ In Cosgrove14, the vector product, S = E x δB/μ₀, is calculated before any averaging or functional fits are applied. In this way, perturbations in the measured E and B are captured more accurately. As pointed out in past studies, variability in the electric field can contribute to the total Joule heat (Codrescu et al. 1995; Cosgrove & Codrescu, 2009). In the standard formulation employed in W05, Joule heat is computed as the mean of <E ²>. However, if there is a high level of fluctuation about the mean of E (i.e., if <|E − < E>|²> is large), then the contribution to Joule heat from the variability is missing if it is assumed that <|E|> represents the total electric field. Codrescu et al. (2000) used radar measurements to calculate the <|E − < E>|²> term, and found that the variability was comparable with the mean value of E. In Cosgrove14, the direct estimate of Joule heat from the measured E attempts to avoid this problem.

Possibly as the result of the methodology, or because the data from which this model is derived is more comprehensive, the model predictions of Poynting flux in the cusp is significantly larger than that forecast by W05. Figure 1.5 (reproduced from Figure 5 in Cosgrove et al., 2014) illustrates the cusp feature for northward IMF, for high (top) and low (bottom) magnetic activity. In this model, the pattern of Poynting flux for high magnetic activity is generally similar to the upper panel of Figure 1.5, regardless of IMF orientation.

Figure 1.5 Cosgrove14 output for high and low magnetic activity for northward IMF. The upper and lower panels have different color bars to prevent saturation. The AL index is shown at center above each panel. The integrated Poynting flux is shown at left above each panel. The Poynting flux for high magnetic activity is similar to that for southward IMF, regardless of actual IMF. IMF clock angle is 0°, magnetic dipole tile angle is 0°, solar wind velocity is 450 km s^‐1, solar wind number density is 4 cm^‐3, and IMF strength in the GSM y‐z plane is 5 nT

(figure and caption reproduced from Cosgrove et al., 2014. Reproduced with permission of John Wiley & Sons).

However the basis of Cosgrove14 is a representation of the high‐latitude Poynting flux by spherical harmonical fits to averages of the measurements. This arrives at the same problem with W05, namely that the model predictions cannot reproduce the highly variable energy input into the IT system characteristic of high magnetic activity. As stated in the paper (Cosgrove et al., 2014), “averaging over a large number of events, as is done to produce this model, will result in significant smearing. Because of this, the model output is not representative of an instant of time, but rather reflects an expected value for each UT, MLT, MLAT, and set of geophysical parameter values.” The Cosgrove14 model, which is relatively new, has yet to undergo the testing and validation that occurred with W05 and previous version of the Weimer models.