Kelvin-Helmholtz waves at the Earth's magnetopause: Multiscale development and associated reconnection

[1] We examine traversals on 20 November 2001 of the equatorial magnetopause boundary layer simultaneously at ∼1500 magnetic local time (MLT) by the Geotail spacecraft and at ∼1900 MLT by the Cluster spacecraft, which detected rolled-up MHD-scale vortices generated by the Kelvin-Helmholtz instability (KHI) under prolonged northward interplanetary magnetic field conditions. Our purpose is to address the excitation process of the KHI, MHD-scale and ion-scale structures of the vortices, and the formation mechanism of the low-latitude boundary layer (LLBL). The observed KH wavelength (>4 × 104 km) is considerably longer than predicted by the linear theory from the thickness (∼1000 km) of the dayside velocity shear layer. Our analyses suggest that the KHI excitation is facilitated by combined effects of the formation of the LLBL presumably through high-latitude magnetopause reconnection and compressional magnetosheath fluctuations on the dayside, and that breakup and/or coalescence of the vortices are beginning around 1900 MLT. Current layers of thickness a few times ion inertia length ∼100 km and of magnetic shear ∼60° existed at the trailing edges of the vortices. Identified in one such current sheet were signatures of local reconnection: Alfvenic outflow jet within a bifurcated current sheet, nonzero magnetic field component normal to the sheet, and field-aligned beam of accelerated electrons. Because of its incipient nature, however, this reconnection process is unlikely to lead to the observed dusk-flank LLBL. It is thus inferred that the flank LLBL resulted from other mechanisms, namely, diffusion and/or remote reconnection unidentified by Cluster.

[1]  A. Miura.  Anomalous transport by magnetohydrodynamic Kelvin‐Helmholtz instabilities in the solar wind‐magnetosphere interaction , 1984 .

[2]  M. Dunlop,et al.  Cluster observations of continuous reconnection at the magnetopause under steady interplanetary magnetic field conditions , 2004 .

[3]  I. Mann,et al.  Finite lifetimes of ideal poloidal Alfvén waves , 1995 .

[4]  A. Miura,et al.  Nonlocal stability analysis of the MHD Kelvin-Helmholtz instability in a compressible plasma. [solar wind-magnetosphere interaction] , 1982 .

[5]  B. Sonnerup,et al.  First results from ideal 2-D MHD reconstruction: magnetopause reconnection event seen by Cluster , 2008 .

[6]  M. Dunlop,et al.  Orientation and motion of two‐dimensional structures in a space plasma , 2005 .

[7]  B. Sonnerup,et al.  Reconstruction of two‐dimensional coherent MHD structures in a space plasma: The theory , 2008 .

[8]  M. Fujimoto,et al.  Vortex-Like Fluctuations in the Magnetotail Flanks and their Possible Roles in Plasma Transport , 2013 .

[9]  S. Chandrasekhar.  Hydrodynamic and Hydromagnetic Stability , 1961 .

[10]  K. Nykyri,et al.  Plasma transport at the magnetospheric boundary due to reconnection in Kelvin‐Helmholtz vortices , 2001 .

[11]  H. Auster,et al.  Turbulent heating and cross‐field transport near the magnetopause from THEMIS , 2008 .

[12]  M. Acuna,et al.  Drift-kinetic Alfvén waves observed near a reconnection X line in the earth's magnetopause. , 2005, Physical review letters.

[13]  G. Chanteur,et al.  Advances in magnetopause Kelvin-Helmholtz instability studies , 1989 .

[14]  David G. Sibeck,et al.  Magnetopause shape as a bivariate function of interplanetary magnetic field Bz and solar wind dynamic pressure , 1993 .

[15]  O. D. Constantinescu,et al.  Magnetic mirror structures observed by Cluster in the magnetosheath , 2003 .

[16]  Christopher T. Russell,et al.  An extended study of the low‐latitude boundary layer on the dawn and dusk flanks of the magnetosphere , 1987 .

[17]  Christopher T. Russell,et al.  ISEE observations of flux transfer events at the dayside magnetopause , 1979 .

[18]  M. Fujimoto,et al.  Recovery of streamlines in the flank low‐latitude boundary layer , 2006 .

[19]  M. Fujimoto,et al.  Reconstruction of a bipolar magnetic signature in an earthward jet in the tail: Flux rope or 3D guide‐field reconnection? , 2007 .

[20]  M. Fujimoto,et al.  Decay of MHD-scale Kelvin-Helmholtz vortices mediated by parasitic electron dynamics. , 2004, Physical review letters.

[21]  J. Steinberg,et al.  Geotail observations of the Kelvin‐Helmholtz instability at the equatorial magnetotail boundary for parallel northward fields , 2000 .

[22]  P. Song,et al.  Signatures of mode conversion and kinetic Alfvén waves at the magnetopause , 2001 .

[23]  J. T. Gosling,et al.  Bifurcated current sheets produced by magnetic reconnection in the solar wind , 2008 .

[24]  Lou‐Chuang Lee,et al.  Magnetic reconnection in the presence of sheared flow and density asymmetry: Applications to the Earth's magnetopause , 1995 .

[25]  A. Hasegawa.  Drift Mirror Instability in the Magnetosphere , 1969 .

[26]  S. Schwartz,et al.  Characteristics of the magnetosheath electron boundary layer under northward interplanetary magnetic field: Implications for high‐latitude reconnection , 2005 .

[27]  Nobuyuki Kaya,et al.  The Low Energy Particle (LEP) Experiment onboard the GEOTAIL Satellite , 1994 .

[28]  Hiroshi Hasegawa,et al.  Grad‐Shafranov reconstruction: An overview , 2006 .

[29]  G. Paschmann,et al.  The magnetosheath region adjacent to the dayside magnetopause: AMPTE/IRM observations , 1994 .

[30]  F. Mozer,et al.  Evidence of diffusion regions at a subsolar magnetopause crossing. , 2002, Physical review letters.

[31]  J. Johnson,et al.  Stochastic ion heating at the magnetopause due to kinetic Alfvén waves , 2001 .

[32]  S. Wing,et al.  2D plasma sheet ion density and temperature profiles for northward and southward IMF , 2002 .

[33]  E. Guirriec,et al.  Early results from the Whisper instrument on Cluster: an overview , 2001 .

[34]  J. Samson,et al.  The spatial development of the low-latitude boundary layer , 1993 .

[35]  A. Vaivads,et al.  Structure of the separatrix region close to a magnetic reconnection X‐line: Cluster observations , 2006 .

[36]  M. Dunlop,et al.  The plasma sheet and boundary layers under northward IMF: A multi-point and multi-instrument perspective , 2008 .

[37]  J. Sauvaud,et al.  Survey of energetic O + ions near the dayside mid-latitude magnetopause with Cluster , 2005 .

[38]  B. Sonnerup,et al.  Two‐dimensional coherent structures in the magnetopause: Recovery of static equilibria from single‐spacecraft data , 1999 .

[39]  M. Fujimoto,et al.  Mode conversion and anomalous transport in Kelvin-Helmholtz vortices and kinetic Alfvén waves at the Earth's magnetopause. , 2007, Physical review letters.

[40]  T. Phan,et al.  Low‐latitude dayside magnetopause and boundary layer for high magnetic shear: 1. Structure and motion , 1996 .

[41]  J. Johnson,et al.  Kinetic Alfvén waves and plasma transport at the magnetopause , 1997 .

[42]  M. Fujimoto,et al.  Magnetic effects on the coalescence of Kelvin-Helmholtz vortices. , 2008, Physical review letters.

[43]  A. Otto,et al.  Magnetic reconnection induced by weak Kelvin‐Helmholtz instability and the formation of the low‐latitude boundary layer , 2006 .

[44]  A. Hasegawa,et al.  Anomalous transport produced by kinetic Alfvén wave turbulence , 1978 .

[45]  M. Fujimoto,et al.  Origin of temperature anisotropies in the cold plasma sheet: Geotail observations around the Kelvin-Helmholtz vortices , 2007 .

[46]  M. Kivelson,et al.  Anomalous aspects of magnetosheath flow and of the shape and oscillations of the magnetopause during an interval of strongly northward interplanetary magnetic field , 1993 .

[47]  A. Vaivads,et al.  Four-point high time resolution information on electron densities by the electric field experiments (EFW) on Cluster , 2001 .

[48]  A. Miura.  Dependence of the magnetopause Kelvin‐Helmholtz instability on the orientation of the magnetosheath magnetic field , 1995 .

[49]  Eos Sorce,et al.  Laboratory for Atmospheric and Space Physics , 2000 .

[50]  I. Papamastorakis,et al.  First multispacecraft ion measurements in and near the Earth's magnetosphere with the identical Cluster ion spectrometry (CIS) experiment , 2001 .

[51]  V. Angelopoulos,et al.  THEMIS multi‐spacecraft observations of magnetosheath plasma penetration deep into the dayside low‐latitude magnetosphere for northward and strong By IMF , 2008 .

[52]  Wolfgang Baumjohann,et al.  The magnetopause for large magnetic shear: AMPTE/IRM observations , 1986 .

[53]  Antonius Otto,et al.  Structure of an MHD‐scale Kelvin‐Helmholtz vortex: Two‐dimensional two‐fluid simulations including finite electron inertial effects , 2008 .

[54]  M. Fujimoto,et al.  Solar wind control of density and temperature in the near‐Earth plasma sheet: WIND/GEOTAIL collaboration , 1997 .

[55]  M. Fujimoto,et al.  Anomalous ion mixing within an MHD scale Kelvin-Helmholtz vortex , 1994 .

[56]  Lou‐Chuang Lee,et al.  Tearing instability, Kelvin‐Helmholtz instability, and magnetic reconnection , 1997 .

[57]  B. Sonnerup,et al.  Minimum and Maximum Variance Analysis , 1998 .

[58]  C. Russell,et al.  Reconnection at the high‐latitude magnetopause during northward interplanetary magnetic field conditions , 2001 .

[59]  M. W. Dunlop,et al.  The Cluster Magnetic Field Investigation: overview of in-flight performance and initial results , 2001 .

[60]  A. Walker.  The Kelvin-Helmholtz instability in the low-latitude boundary layer , 1981 .

[61]  H. Hasegawa,et al.  Transport of solar wind into Earth's magnetosphere through rolled-up Kelvin–Helmholtz vortices , 2004, Nature.

[62]  Tetsuya T. Yamamoto,et al.  A linear analysis of the hybrid Kelvin‐Helmholtz/Rayleigh‐Taylor instability in an electrostatic magnetosphere‐ionosphere coupling system , 2008 .

[63]  Zhen Liu,et al.  Generation of vortex‐induced tearing mode instability at the magnetopause , 1990 .

[64]  V. Angelopoulos,et al.  Magnetic island formation between large‐scale flow vortices at an undulating postnoon magnetopause for northward interplanetary magnetic field , 2009 .

[65]  M. Wiltberger,et al.  Solar wind driving of magnetospheric ULF waves: Pulsations driven by velocity shear at the magnetopause , 2008, 1010.3998.

[66]  K. Ogilvie,et al.  The Kelvin‐Helmholtz instability at the magnetopause and inner boundary layer surface , 1989 .

[67]  A. Miura.  Compressible magnetohydrodynamic Kelvin–Helmholtz instability with vortex pairing in the two-dimensional transverse configuration , 1997 .

[68]  A. Miura.  Self-Organization in the Two-Dimensional Kelvin-Helmholtz Instability , 1999 .

[69]  C. Owen,et al.  In situ evidence of magnetic reconnection in turbulent plasma , 2007 .

[70]  Christopher T. Russell,et al.  Initial ISEE magnetometer results - Magnetopause observations , 1978 .

[71]  M. Fujimoto,et al.  Geotail observations of the dayside outer boundary region: Interplanetary magnetic field control and dawn‐dusk asymmetry , 2003 .

[72]  S. Fuselier,et al.  Tracing ions in the cusp and low‐latitude boundary layer using multispacecraft observations and a global MHD simulation , 2002 .

[73]  Manuel Grande,et al.  PEACE: A PLASMA ELECTRON AND CURRENT EXPERIMENT , 1997 .

[74]  I. Papamastorakis,et al.  Magnetopause properties from AMPTE/IRM observations of the convection electric field: Method development , 1987 .

[75]  M. Dunlop,et al.  Reconstruction of two-dimensional magnetopause structures from Cluster observations: verification of method , 2004 .

[76]  C. Russell,et al.  Model of the formation of the low-latitude boundary layer for strongly northward interplanetary magnetic field , 1992 .

[77]  C. T. Russell,et al.  Initial ISEE magnetometer results: magnetopause observations , 1978 .

[78]  L. Rezeau,et al.  Magnetopause reconnection induced by magnetosheath Hall‐MHD fluctuations , 2001 .

[79]  H. Hasegawa,et al.  Dense and stagnant ions in the low‐latitude boundary region under northward interplanetary magnetic field , 2004 .

[80]  T. Carozzi,et al.  First results of electric field and density observations by Cluster EFW based on initial months of operation , 2001 .

[81]  C. Torrence,et al.  A Practical Guide to Wavelet Analysis. , 1998 .

[82]  B. Sonnerup.  Theory of the low-latitude boundary layer , 1980 .

[83]  A. Vaivads,et al.  Structure of the magnetic reconnection diffusion region from four-spacecraft observations. , 2004, Physical review letters.

[84]  M. Fujimoto,et al.  Single-spacecraft detection of rolled-up Kelvin-Helmholtz vortices at the flank magnetopause , 2006 .

[85]  C. Owen,et al.  Evolution of Kelvin‐Helmholtz activity on the dusk flank magnetopause , 2008 .

[86]  Y. D. Hu,et al.  Local magnetic reconnection caused by vortices in the flow field , 1988 .

[87]  M. Fujimoto,et al.  Kelvin-Helmholtz instability in a magnetotail flank-like geometry: Three-dimensional MHD simulations , 2006 .

[88]  I. Dandouras,et al.  Electron density estimations derived from spacecraft potential measurements on Cluster in tenuous plasma regions , 2008 .

[89]  S. Schwartz.  Shock and Discontinuity Normals, Mach Numbers, and Related Parameters , 1998 .

[90]  Masahiro Hoshino,et al.  Onset of turbulence induced by a Kelvin‐Helmholtz vortex , 2004 .

[91]  C. Russell,et al.  The thickness of the magnetopause current layer: ISEE 1 and 2 observations , 1982 .

[92]  E. W. Hones,et al.  Structure of the low‐latitude boundary layer , 1980 .

[93]  C. Farrugia,et al.  Concerning a problem on the Kelvin‐Helmholtz stability of the thin magnetopause , 2004 .

[94]  A. Lui,et al.  Auroral bright spots on the dayside oval , 1989 .