Statistical Modeling of the Coupled F‐Region Ionosphere‐Thermosphere at High Latitude During Polar Darkness

• Published in: Journal of geophysical research. Space physics Vol. 124; no. 2; pp. 1389 - 1409
• Main Authors: Dorrian, G. D., Wood, A. G., Ronksley, A., Aruliah, A., Shahtahmassebi, G.
• Format: Journal Article
• Language: English
• Published: 01.02.2019
• Subjects: climatology; ionosphere plasma; ionosphere‐thermosphere coupling; Joule heating; linear modeling; space weather
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2018JA026171

Statistical models have been developed for predicting the behavior of the coupled high‐latitude ionosphere‐thermosphere system. The modeled parameters were the F‐layer peak electron density, plasma structuring, ion temperature, neutral temperature, and the difference between these temperatures, which is a key term in the Joule heating equation. Ionospheric measurements from the European Incoherent Scatter Svalbard Radar and neutral atmosphere measurements from the colocated University College London Fabry‐Perot Interferometers have been made across a solar cycle. These data were all acquired during nighttime conditions as the observations with the Fabry‐Perot Interferometers are restricted to such times. Various geophysical proxies were tested to represent the processes that influence the modeled parameters. The dominant geophysical proxy for each modeled parameter was then determined. Multivariate models were also developed showing the combinations of parameters that best explained the observed variability. A comparison with climatology showed that the models give an improvement in every case with skill scores based on the mean square error of up to 0.88. Plain Language Summary The upper atmosphere of the Earth is a mixture of partially ionized plasma (the ionosphere) and neutral gases (the thermosphere). The plasma is comprised of charged particles which are subject to electromagnetic forces, whereas the neutral thermosphere is not. These two populations are the coupled ionosphere‐thermosphere. Plasma density in the ionosphere is controlled by plasma production mechanisms such as solar ultraviolet illumination, plasma loss mechanisms such as collision induced recombination, and transport mechanisms such as variability in the geomagnetic field. Of particular interest is the process of heat transfer from ionospheric plasma to the neutral thermosphere, so‐called Joule heating. Combined with geophysical information, such as the Kp index, variability in the interplanetary magnetic field, and season, this study presents a series of statistical linear models that rank various physical effects in terms of how strongly they influence the behavior of the coupled ionosphere‐thermosphere at high latitude during polar darkness. These models also show which combinations of physical effects enable predictions to be made of observed ionosphere‐thermosphere behavior, to a greater accuracy than by a climatological approach. This study was made possible using ionosphere data collected from the European Incoherent Scatter Svalbard radar with neutral thermosphere observations from a colocated Fabry‐Perot Interferometer. Key Points Linear modeling of variability in the high‐latitude coupled ionosphere‐thermosphere is a more accurate predictor than climatology Univariate linear models demonstrate the relative influences of different geophysical proxies on ionosphere‐thermosphere variability