Teoría y Simulación de la Actividad de Kelvin–Helmholtz en la Magnetopausa Terrestre en el Evento del 7 de diciembre de 2000

GRATTON, F. T.

Anales de la Academia Nacional de Ciencias de Buenos Aires, Tomo XL

ANCBA

Lugar: Buenos Aires; Año: 2006; p. 57 - 80

Theory and simulations associated to observations from ACE, and CLUSTER are brought to bear to study large oscillations and waves at the magnetopause (MP) on December 7, 2000. A phase of the event is characterized by an interplanetary tangential discontinuity (TD) followed by a lapse of northward interplanetary magnetic field. The TD was both a current sheet and a vorticity layer, causing rotation of field and velocity planar components, while the normal pressure and the solar wind dynamic pressure remained constant. Arrival of the TD and its concomitant perturbations caused large-amplitude »4 min oscillations of the MP, followed for »10 minutes by shorter-period (90 s) large-amplitude oscillations in all quantities registered by CLUSTER on an outbound crossing of the duskside boundary layer. A stability analysis based on input parameters suggested by the spacecraft data, and a nonlinear numerical simulations with a new 3D+t MHD code of arbitrary Lagrangian - Eulerian and finite volume class, are presented. Both studies confirm the presence of MP surface waves of Kelvin-Helmholtz (KH) origin, after the initial large undulatory motions. The KH activity not only causes the roll-over of the boundary layer original positive vorticity into co-rotating vortices, but generates also negative counter-rotating vortices of similar strength. The results brings into light novel features of the process that broadens and deforms the configuration of the low latitude boundary layer, favoring the enhancement of plasma diffusion through the magnetopause. It is also concluded that the impact of the TD and its disturbances abbreviate the development of the instability, hastening the non-linear development of KH vortices.