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

Abstract

[1] Results from the three-dimensional nonlinear simulations of the gradient drift instability to study structuring in high-latitude plasma patches are presented. Simulations demonstrate that the existence of the mesoscale structures (10 km to 100 m) on both leading and trailing edges and inside a patch is due to (1) the nonlinear development of the gradient drift instability (GDI) or due to (2) occasional reversal of the direction of convection. The high-resolution simulation data have a dynamic range that allows us to make detailed comparisons with the observed density and velocity fluctuation spectra. We use the measured ion density and horizontal velocity data from the Dynamic Explorer 2 (DE 2) spacecraft examined by Kivanç and Heelis [1997] to compare them with our simulations. Density structures in the leading and trailing edges of patches have been examined, and comparison of statistical characteristics of the average density gradient on these edges with those in the work by Coley and Heelis [1998] has been performed. The dynamics and evolution of the density fluctuations over the realistic time scale are shown, thereby providing a significant evidence of the existence of the GDI at high latitudes as a structure-generating mechanism and a first principle understanding of the hierarchy of the instabilities involved in the observed structuring in high-latitude plasma patches.

Dependence of the high-latitude plasma irregularities on the auroral activity indices: a case study of 17 March 2015 geomagnetic storm

“…A polar cap patch typically has a density that is 2-20 times larger than the surrounding background electron density and its horizontal size ranges from 100 to 1000 km (e.g., Tsunoda 1988, Crowley et al 2000. The convecting patches develop intermediate-scale irregularities by action of the gradient-drift instability mechanism (Kersley et al 1995), that is also confirmed by numerical simulation (Gondarenko and Guzdar 2004). Because of the steep plasma density gradients and irregularities at their edges (Weber et al 1986), the TOI structure and polar cap patches can be detected with GPS measurements (e.g., Aarons 1997;Noja et al 2013;van der Meeren et al 2014).…”

Dynamics of high-latitude patches and associated small-scale irregularities during the October and November 2003 storms

“…The most often referenced explanation is the effect of neutral winds, which may be very important at high latitudes, especially during substorm activity and in the regions where the convective plasma flow is not uniform, e.g., close to the boundaries of auroral oval (Tsunoda, 1988). Recently, Gondarenko and Guzdar (2004) performed the threedimensional simulations of the gradient drift instability to study structuring of patches. They have shown that instability originating at the trailing edge of patches in the later phase of the nonlinear evolution spreads over the whole patch.…”

Toward an integrated view of ionospheric plasma instabilities: Altitudinal transitions and strong gradient case

“…Solving the full electron momentum equation in fully numerical modeling efforts is computationally intensive, and this is one reason why the electron continuity equation and the vorticity equation are often used in modeling of plasma structuring processes [Gondarenko and Guzdar, 2004]. In the above analysis, both were included or excluded.…”