Large amplitude perturbations and waves at the duskside LLBL of the magnetopause generated by an interplanetary tangential discontinuity on December 7, 2000

On December 7, 2000 a joint current sheet and vorticity layer hit the magnetopause (MP) generating large amplitude oscillations, and wave-like perturbations observed by CLUSTER at the near dusk flank. Linear stability theory and MHD numerical simulations support the hypothesis that the waves were due to the Kelvin-Helmholtz (KH) instability. The simulation brings into light novel dynamical properties of the boundary layer under the KH excitation.Fil: Gratton, Fausto Tulio Livio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Farrugia, C. J.. University of New Hampshire at Manchester; Estados UnidosFil: Bilbao, Luis Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Gnavi, Graciela Delia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Lund, E. J.. University of New Hampshire at Manchester; Estados Unido

The magnetosphere mixing layer: Observations, MHD stability, and large eddy simulations

The work is about the evolution of large vortices in the boundary layer of the terrestrial magnetopause studied by computational physics, in support of interpretive analysis of spacecraft data from an event observed on December 7, 2000. The distinctive features of the configuration examined are i) the very small magnetic shear across the boundary, and ii) the dynamics concerns mainly the vorticity. The magnetic field is only fluted during the process, but it determines the direction of the vortex axis. Considering new elements from computer simulations and observations, an extension of the research of a recent publication in this journal is reported. A magnetohydrodynamic code for large eddy simulations is used to examine the influence of supersonic, and superAlfvénic speeds, on the dynamics of the boundary layer. Correlations of data are studied to identify signatures of the Kelvin-Helmholtz instability, and the presence of whirling plasma. The aim is to improve the understanding of factors that govern the tailward growth of the low latitude boundary layer, and the potentiality of plasma entry into the magnetosphere, during periods of northward interplanetary magnetic field.Fil: Gratton, Fausto Tulio Livio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Bilbao, Luis Ernesto. Pontificia Universidad Católica Argentina ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Gnavi, Graciela Delia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Farrugia, C. J.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentin

The KH stability of the supersonic magnetopause flanks modeled by continuous profiles for the transition

Two examples of stability analysis of the supersonic magnetopause (MP) flanks, based on compressible, ideal MHD theory are reported. The input parameters for local MP models are derived from spacecraft crossings data. The results emphasize the sensitivity of the Kelvin-Helmholtz instability on fine structure features of the boundary layer.Fil: Gnavi, Graciela Delia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Gratton, Fausto Tulio Livio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Farrugia, C. J.. University of New Hampshire at Manchester; Estados UnidosFil: Bilbao, Luis Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; Argentin

Two-stage oscillatory response of the magnetopause to a tangential discontinuity/vortex sheet followed by northward IMF: Cluster observations

We discuss the motion and structure of the magnetopause/boundary layer observed by Cluster in response to a joint tangential discontinuity/vortex sheet (TD/VS) observed by the Advanced Composition Explorer spacecraft on 7 December 2000. The observations are then supplemented by theory. Sharp polarity reversals in the east-west components of the field and flow By and V y occurred at the discontinuity. These rotations were followed by a period of strongly northward interplanetary magnetic field (IMF). These two factors elicited a two-stage response at the magnetopause, as observed by Cluster situated in the boundary layer at the duskside terminator. First, the magnetopause suffered a large deformation from its equilibrium position, with large-amplitude oscillations of ∼3-min period being set up. These are argued to be mainly the result of tangential stresses associated with ΔV ythe contribution of dynamic pressure changes being small in comparison. This strengthens recent evidence of the importance to magnetospheric dynamics of changes in azimuthal solar wind flow. The TD/VS impact caused a global response seen by ground magnetometers in a magnetic local time range spanning at least 12 h. The response monitored on ground magnetometers is similar to that brought about by magnetopause motions driven by dynamic pressure changes. Second, Cluster recorded higher-frequency waves (∼79 s). Two clear phases could be distinguished from the spectral power density, which decreased by a factor of ∼3 in the second phase. Applying compressible linearized MHD theory, we show that these waves are generated by the Kelvin-Helmholtz (KH) instability. Varying the local magnetic shear at the Cluster locale, as suggested by the temporal profile of the IMF clock angle, we find that locally stability was reinstated, so that the reduced power in the second phase is argued to be due residual KH activity arriving from locations farther to the dayside. Copyright 2008 by the American Geophysical Union.Fil: Farrugia, C. J.. University Of New Hampshire Durham;Fil: Gratton, Fausto Tulio Livio. Universidad de Buenos Aires; Argentina. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Lund, E.J.. University Of New Hampshire Durham; Reino UnidoFil: Sandholt, P.E.. University of Oslo; NoruegaFil: Cowley, S.W.H.. University of Leicester; Reino UnidoFil: Torbert, R.B.. University Of New Hampshire Durham; Reino UnidoFil: Gnavi, Graciela Delia. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Mann, I.R.. University of Alberta; CanadáFil: Bilbao, Luis Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física del Plasma. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física del Plasma; ArgentinaFil: Mouikis, C.. University Of New Hampshire Durham; Reino UnidoFil: Kistler, L.. University Of New Hampshire Durham; Reino UnidoFil: Smith, C.W.. University Of New Hampshire Durham;Fil: Singer, H.J.. National Oceanic And Atmospheric Administration; Estados UnidosFil: Watermann, J.F.. Danmarks Meteorologiske Institut; Dinamarc