Parametric dependence of electric field variability in the Sondrestrom database: A linear relation with Kp

Abstract

[1] Motivated by the question of the auroral region contribution to thermospheric heating, the database from the Sondrestrom incoherent scatter radar is used to study the variability of the high-latitude vector electric field. The ability of various geophysical parameters to describe the variability is evaluated, using a minimum variance criterion, and it is found that the standard deviation ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffihjẼ À hẼij 2 i q scales linearly with Kp. It is also found that magnetic latitude and magnetic local time are important descriptors and that the specific dependance largely agrees with variability measurements made by the DE 2 satellite, even though the latter measurements probe a much higher frequency range. A number of other parameters are found to be less important as descriptors, including the IMF clock angle and the season. Thermospheric global circulation models currently incorporate an auroral zone heat source in the form of Joule heating associated with the mean electric field hẼi, where the mean is taken over temporal and spatial scales below the models resolution. However, comparison of the modeling outputs with MSIS suggests that the auroral zone heat source is underestimated. Because it is the mean of the squared electric field that determines Joule heating and not the square of the mean, the electric field variability ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffihjẼ À hẼij 2 i q has been put forward as the missing source. Our results indicate that this heat source may be parameterized by Kp, which carries the further implication that the variability is associated with a global-scale phenomenon.

Empirical model of Poynting flux derived from FAST data and a cusp signature

“…The cusp feature that we find is mostly absent in the Poynting flux maps derived from separate models of the electric and magnetic fields [ Weimer , ]. As found by Cosgrove and Thayer [], using data from the Sondrestrom radar, the cusp is associated with a high degree of electric field variability. Thus, capturing the Poynting flux associated with the cusp probably requires a direct Poynting flux model.…”

“…The Weimer [] empirical Poynting flux model is formed by combining separate models of the electric and magnetic potentials, and therefore may suffer to the extent that fluctuations in these quantities are correlated. It appears that this becomes an issue in the cusp, where the electric field variability is high [ Cosgrove and Thayer , ], and where the Weimer [] model does not show a significant contribution. For southward IMF, the hemispherically integrated Poynting flux predicted by our model is about 20% larger than predicted by Weimer [], which is likely within the model error.…”

“…They found that the variability was on the order of the mean. The Codrescu et al [] and Codrescu et al [] studies inspired a number of subsequent studies: Crowley and Hackert [] analyzed outputs from the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure [ Richmond and Kamide , ]; Matsuo et al [, ], Matsuo and Richmond [], and Deng et al [] analyzed data from the Dynamics Explorer 2 (DE‐2) satellite [ Hanson et al , ; Heelis et al , ]; Shepherd et al [] analyzed data from the Super Dual Auroral Radar Network radars [e.g., Greenwald , ]; Cosgrove and Thayer [] analyzed data from the Sondrestrom incoherent scatter radar, and Deng and Ridley [] explored different resolutions within the Global Ionosphere Thermosphere Model [ Ridley et al , ].…”

Effects of high‐latitude ionospheric electric field variability on global thermospheric Joule heating and mechanical energy transfer rate

“…These studies have shown that the electric field variability characterized as the standard deviation is of significant magnitude, often as large as the mean itself. Cosgrove and Thayer [2006] have shown the magnitude of the variability, measured in terms of the standard deviation estimated from the Sondrestrom incoherent scatter radar plasma drift measurements, scales linearly with the Kp index. Regarding the temporal variation of the electric field, Crowley and Hackert [2001] conducted a spectrum analysis of AMIE convection patterns and concluded that a majority of the variability arises from variations with periods less than 1 hour.…”

Comparison of AMIE‐modeled and Sondrestrom‐measured Joule heating: A study in model resolution and electric field–conductivity correlation

“…They found that the variability was on the order of the mean. The Codrescu et al [1995] and Codrescu et al [2000] studies inspired subsequent studies by Crowley and Hackert [2001], by Matsuo et al [2003, 2005] and Matsuo and Richmond , 2008], by Shepherd et al [2003], and by Cosgrove and Thayer [2006], utilizing the Assimilative Mapping of Ionospheric Electrodynamics (AMIE) procedure [ Richmond and Kamide , 1988], DE2 satellite data [ Hanson et al , 1981; Heelis et al , 1981], SuperDARN [e.g., Greewald , 1995], and the Sondrestrom incoherent scatter radar, respectively. For more complete summaries of previous research on variability, see Matsuo et al [2003] and Johnson and Heelis [2005].…”