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Investigation of the Gradient Drift Instability as a Cause of Density Irregularities in Subauroral Polarization Streams
Author(s) -
Rathod C.,
Srinivasan B.,
Scales W.,
Kunduri B.
Publication year - 2021
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2020ja029027
Subject(s) - turbulence , instability , velocity gradient , density gradient , mechanics , physics , drift velocity , shear (geology) , ionosphere , geophysics , clear air turbulence , computational physics , plasma , geology , quantum mechanics , petrology
Density irregularities have been observed in subauroral polarization streams (SAPS). One hypothesis of the cause of this ionospheric turbulence, based on the background morphology, is the gradient drift instability (GDI). This work models the GDI using a two‐dimensional electrostatic fluid model to determine if it is a viable cause of turbulence generation in SAPS. A statistical study of different velocity profiles, based on SuperDARN radar and Global Positioning System total electron content data, is used to prescribe parameters in the numerical model. The parameter space of different SAPS profiles is explored to study the effect on GDI development. As the velocity shear is initialized closer to the unstable density gradient, the GDI becomes increasingly damped. For these cases, the density and electric potential turbulence cascades obtained from the numerical model follow power laws of about −5/3 or −2, which is in agreement with observational data. If the region of sheared velocity overlaps the density gradient, the GDI becomes stabilized. The latitudinal location of maximum GDI growth depends on the density profile, the velocity profile, and the neutral wind direction. Using velocity profiles with regions of low velocity shear can cause instabilities that grow inside SAPS which have turbulence cascades with different behavior. In all parameter regimes considered, the GDI turbulence is precluded from extending through regions of velocity shear. Turbulence is generated for a variety of SAPS relevant conditions; therefore, the GDI has been shown to be a viable candidate for generating ionospheric irregularities in SAPS.