Turbulent times in the northern polar ionosphere?

Abstract

[1] A model is presented of the growth rate of turbulently generated irregularities in the electron concentration of northern polar cap plasma patches. The turbulence is generated by the short-term fluctuations in the electric field imposed on the polar cap ionosphere by electric field mapping from the magnetosphere. The model uses an ionospheric imaging algorithm to specify the state of the ionosphere throughout. The growth rates are used to estimate mean amplitudes for the irregularities, and these mean amplitudes are compared with observations of the scintillation indices S 4 and s by calculating the linear correlation coefficients between them. The scintillation data are recorded by GPS L1 band receivers stationed at high northern latitudes. A total of 13 days are analyzed, covering four separate magnetic storm periods. These results are compared with those from a similar model of the gradient drift instability (GDI) growth rate. Overall, the results show better correlation between the GDI process and the scintillation indices than for the turbulence process and the scintillation indices. Two storms, however, show approximately equally good correlations for both processes, indicating that there might be times when the turbulence process of irregularity formation on plasma patches may be the controlling one.

A comparison of the relative effect of the Earth's quasi‐DC and AC electric field on gradient drift waves in large‐scale plasma structures in the polar regions

“…The AC component of the electric field is comparable to or larger than the quasi‐DC component in 94% of the orbit segments found that likely traverse large‐scale plasma structures in the polar regions. This fact both supports and greatly strengthens the conclusions of Burston et al [], namely, that KKT can be as or more important than the GDI with regard to structuring of patches. The knowledge that KKT can often be as energetic a process as the GDI and can occur anywhere on the patch, rather than in a preferred location (trailing edge) affords a better explanation of the examples observed in Kivanc and Heelis [] of fully structured patches and patches with structure on the leading and trailing edges.…”

“…A number of explanations for the mechanism of irregularity formation within polar cap plasma patches and large-scale plasma structures in the polar regions have been proposed, including the current convective instability (CCI), first suggested in relation to auroral structures [Ossakow and Chaturvedi, 1979] and in plasma patches by Kelley [2009], the primary Kelvin-Helmholtz Instability (KHI) (possibly in conjunction with other processes) [e.g., Carlson et al, 2007;Gondarenko and Guzdar, 2006a;Oksavik et al, 2012], the gradient drift instability (GDI) [e.g., Basu et al, 1990;Burston et al, 2009;Chaturvedi et al, 1994;Gondarenko, and Guzdar, 2006b;Kivanc and Heelis, 1997;Weber et al, 1984] and a related "turbulent" process [Kelley and Kintner, 1978], which we term Kelley-Kintner-Turbulence (KKT). The term "turbulence" comes from magnetospheric electric fields that are turbulent in that they show continual variation at short time scales, and these fluctuations are also mapped to the ionosphere, exposing plasma to rapidly varying E × B drifts that can cause gradient drift instabilities, generating turbulent mixing of the plasma, if there is an electron concentration gradient present [Burston et al, 2010] Using Dynamics Explorer 2 satellite observations [Burston et al, 2016] investigated the range of possible values for the linear growth rates for each of these processes. In that study, we found that the inertial KKT instability gave rise to the largest growth rates followed by those for inertial gradient drift, collisional turbulence and collisional shortwave current convective instabilities.…”

Characteristics of GPS TEC variations in the polar cap ionosphere

“…Other suggestions of patch origin include external plasma sources such as ionization due to precipitation from the cusp region [ Walker et al ., ], density depletion in the cusp region due to enhanced plasma recombination resulting from ion heating [ Tsunoda , ], or from auroral region precipitation of the dawnside convection cell, where ionospheric plasma is exposed to precipitation for long durations due to the corotation effect [ MacDougall and Jayachandran , ]. Several studies have reported GPS TEC observations of polar cap patches [e.g., Burston et al ., ; Krankowski et al ., ], with reported TEC enhancements of up to 10–15 TECU. Magnitude, spatial scales, and temporal scales of electron density variations associated with patches can be quite random, typically resulting in lower frequency (<2 mHz) variations in TEC.…”

Statistics of ionospheric disturbances and their correlation with GNSS positioning errors at high latitudes

“…Weber et al 1986;Kersley et al 1995;Aarons 1997;Kivanc & Heelis 1997;Aquino et al 2005;Krankowski et al 2006;Skone et al 2009;Spogli et al 2009;Burston et al 2010;Tiwari et al 2010;Prikryl et al 2013). It has been observed that phase scintillation occurs more often than amplitude scintillation at high latitudes, and that scintillation is more common on geomagnetically disturbed days in the auroral oval region and close to noon and midnight (Aquino et al 2005;Spogli et al 2009;Prikryl et al 2010;Tiwari et al 2010;Moen et al 2013;Prikryl et al 2013).…”