Large Scale Vortices in the Magnetospheric Boundary Layer

GRATTON, F. T.; BILBAO, L. E.; GNAVI, G.; FARRUGIA, C. J.

Anales de la Academia Nacional de Ciencias de Buenos Aires

ANCBA

Lugar: Buenos Aires; Año: 2011; p. 239 - 263

We report the results of increasing the speed of the magnetosheath plasma to supersonic and superalfvénic levels on the dynamics of large vortices formed in the boundary layer of the terrestrial magnetopause. The study is based on computational magneto-fluid dynamics. The boundary layer model is designed with spacecraft data (Cluster mission) observed on December 7, 2000. The distinctive features of this configuration are a) very small magnetic shear across the boundary, and b) the physical activity concerns mainly the vorticity; the magnetic field is only fluted during the process, but it determines the direction of the vortex axis and other features. In addition, we analize correlations of data to identify signatures of the Kelvin-Helmholtz instability, and the presence of a whirling plasma in the boundary layer. The new results extend an earlier investigation presented at this Academy (Anales,Vol. XL, 2007) along two lines: i) the magnetosheath flow increase up to supersonic and super-Alfvénic speeds on vortex simulations; ii) the analysis of data correlations that may disclose the existence of a vortical boundary layer. The purpose is to contribute to the elucidation of factors that govern the plasma entry into the magnetosphere during periods of northward interplanetary magnetic field.