Modeled F region response to auroral dynamics based upon Dynamics Explorer auroral observations

Abstract

Auroral images from the Dynamics Explorer 1 (DE 1) scanning auroral imager have been combined with in situ auroral precipitation data from the DE 2 low altitude plasma instrument to form a time‐dependent global auroral energy flux model. This model has both good time (12 min) and spatial (100 km) resolution compared to that currently available for global scale ionospheric and thermospheric modeling. The development and comparison of this model with others are discussed. Data from an aurorally active period, November 25, 1981, are presented and used as a case study for this model. Using a global ionospheric model, the effect of the DE auroral model is contrasted with that of a conventional empirical auroral energy flux model. Major differences in the modeled F region ionosphere are predicted from this comparative study. Specifically, F region densities differ by factors of two to four, while density boundary locations differ by up to 5° in latitude. The results indicate that “pixel size” auroral fine‐structure must be included in the global ionosphere and thermosphere models when they are tested against specific ground‐based or satellite data sets if an unambiguous result is to be obtained. The longer time constants of the F region are not enough to smooth‐out the auroral (spatial and temporal) dynamics.

Global Auroral Morphology: Quadrennial Report to the I.U.G.G. on U.S. Contributions

“… Hardy et al ., [1987] have ordered their data versus Kp, while Fuller‐Rowell and Evans [1987] have ordered their data according to an auroral activity index related to the total hemispherical energy inputs. It is interesting to compare these statistical results with the results of Sojka et al . [1989] who have derived a global auroral energy flux model based not on statistical results but on the relatively new technique of multispectral global auroral imaging (see later discussions).…”

“…Recently there has been very substantial efforts at learning how to extract the properties of precipitating particles (thus inferring other parameters such as conductivity) by using the multispectral properties of remotely sensed auroral emissions: e.g. Ishimoto et al , [1988], Rees and Lummerzheim [1989], Robinson et al , [1989], Steele and McEwen [1990], Richards and Torr [1990], and Sojka et al . [1989].…”

Global scale, physical models of the F region ionospere

“…Craven and Frank [1987] have demonstrated how these images can be used to give detailed spatial and temporal variations of the auroral oval during storm periods. Sojka et al [1989] have used such images to define the entire northern auroral oval over a 3-hour storm period. The images are used to deduce the precipitating energy flux, auroral boundaries to -_100 km resolution, and a time resolution of 12 min.…”

“…The images are used to deduce the precipitating energy flux, auroral boundaries to -_100 km resolution, and a time resolution of 12 min. In their initial study, Sojka et al [1989] show how sensitive the ionosphere is to auroral structures.…”

An Empirical Model of FUV Auroral Intensity

“…The purpose is (1) to create a statistical model of Far Ultraviolet (FUV) auroral emissions and (2) to relate this model to a statistical model of particle precipitation into the high-latitude ionosphere. The first objective is to create a model that is neither a mathematical representation [Holzworth et al, 1975;Meng et al, 1977] nor an instantaneous 'snapshot' of the auroral oval [Sojka et al, 1989]. The empirical model is to delineate the average position and intensity of the auroral oval and other cruissions of the high-latitude region at various levels of magnetic activity.…”