Density and electric field fluctuations associated with the gradient drift instability in the high‐latitude ionosphere

Abstract

[1] The magnitudes of the density and electric field fluctuations and their spectral characteristics were studied with a three-dimensional nonlinear model of the structuring in high-latitude patches caused by the primary gradient drift instability. The simulations were compared with the simultaneous density and electric field spectra obtained from noon-midnight and dawn-dusk orbits of the Dynamic Explorer 2 (DE 2) satellite [Basu et al., 1990]. The magnitudes of the simulated density and electric field fluctuations were found to be in very good agreement with the measured data. In the directions parallel and perpendicular to convection, the similarities in the spectral slope distributions of both simulated and observed density and electric field fluctuations were demonstrated. These findings together with our earlier results [Gondarenko and Guzdar, 1999, 2001] provide a significant evidence for coexistence of the primary gradient drift instability and subsequent secondary Kelvin-Helmholtz and tertiary shear-flow instabilities.

Plasma patch structuring by the nonlinear evolution of the gradient drift instability in the high‐latitude ionosphere

“…Although spectral characteristics of the observed plasma structures are found to be consistent with those provided by the numerical simulations of the GDI [ Gondarenko and Guzdar , 2004], it is understood that there are various structure‐producing mechanisms at high latitudes. The investigation of the averaged irregularity amplitudes and spectral indices can help to identify the dominant mechanism of the mesoscale structuring.…”

“…The high‐resolution data from our simulations were compared with the observations of the simultaneous density Δ N / N and electric field Δ E fluctuations in the directions parallel and perpendicular to the plasma patch convection [ Basu et al , 1990]. Our recent results [ Gondarenko and Guzdar , 2004] demonstrated the similarities in the spectral slope distributions of both simulated and observed density and electric field spectra in the directions parallel and perpendicular to convection. The magnitudes of the simulated density and electric field fluctuations were found to be in agreement with the measured data.…”

“…In Table 1 we present a comparison of spectral indices of the simulated Δ N / N and Δ E and spectral characteristics of the measured DE 2 data [ Basu et al , 1990]. Shown are the mean values of the numerically computed distributions of spectral indices of Δ N / N and Δ E [ Gondarenko and Guzdar , 2004].…”

“…Most recently, Gondarenko and Guzdar [2004] have studied the magnitudes and spectral characteristics of the density and electric field fluctuations obtained with the 3‐D model of the nonlinear evolution of the GDI and subsequent secondary instabilities. In the directions parallel and perpendicular to convection, the similarities in spectral slope distributions of both simulated [ Gondarenko and Guzdar , 2004] and observed [ Basu et al , 1990] density and electric field fluctuations were demonstrated. The amplitudes of the simulated density fluctuations Δ N / N and the relation between the magnitudes of the electric field Δ E and Δ N / N were found to be in agreement with the measured characteristics reported by Basu et al [1990].…”

Studies of the Origin and Evolution of Ionospheric Irregularities and Their Effects on AF Systems

“…Early observations of the scintillations associated with polar cap patches have pointed out that the gradient drift instability (GDI) is responsible for the onset of km-scale irregularities [Weber et al, 1986;Basu et al, 1988]. While the linear GDI is only unstable on the trailing edge of the patch, in the non-linear regimen GDI predicts structures that propagate from the unstable edge, through the patch and reach the stable edge [Gondarenko et al, 2003;Gondarenko and Guzdar, 2004]. Similarly, if a velocity reversal or plasma stirring occurs along the patch trajectory then other sides of the patch could develop plasma structures.…”