Ion injections and magnetic field oscillations near the high‐latitude magnetopause associated with solar wind dynamic pressure enhancement

[1] The characteristics of particles and magnetic fields associated with a step-like enhancement in solar wind dynamic pressure are investigated by using observations from the Polar spacecraft. At the time, Polar was located near its apogee of ∼9 RE at high latitude in the afternoon sector. Impulsive, energy-dispersed injections of ions were observed by Polar in both parallel and antiparallel pitch angle directions, with a much shorter duration in the parallel direction (toward the Earth) than in the antiparallel direction (away from the Earth). The energies of the injected ions ranged from ∼200 eV to a few keV, and they are considered of magnetosheath origin. The energy dispersion of the injected ions is consistent with the interpretation of the velocity filter or time-of-flight effect as the magnetosheath ions enter the magnetosphere and propagate downward and then are mirrored at low altitude where magnetic field lines converge. It is estimated that the entrance of the magnetosheath ions was located ∼3.9–7.5 RE away from Polar, and the distance from the spacecraft to the mirror point was ∼7.7–8.1 RE, corresponding to ∼830–3600 km in altitude. The Polar data clearly favor magnetic reconnection as the primary mechanism for the transport of magnetosheath plasmas into the magnetosphere. A good correspondence is found between the magnetic field oscillation and the intermittence of the ion injections, implying that the impulsive ion injections were a consequence of the intermittent magnetic reconnection at the high-latitude magnetopause that had been modulated by compressional waves produced by the solar wind dynamic pressure enhancement.

[1]  M. Dunlop,et al.  Evidence for impulsive solar wind plasma penetration through the dayside magnetopause , 2003 .

[2]  M. Fujimoto,et al.  A study of ion injections at the dawn and dusk polar edges of the auroral oval , 2001 .

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

[4]  M. Dunlop,et al.  Cluster observations of the high-latitude magnetopause and cusp: initial results from the CIS ion instruments , 2001 .

[5]  J. Lyon,et al.  Response of the ionosphere to a density pulse in the solar wind: Simulation of traveling convection vortices , 1999 .

[6]  J. Rouzaud,et al.  The ion experiment onboard the Interball-Aurora satellite; initial results on velocity-dispersed structures in the cleft and inside the auroral oval , 1998 .

[7]  J. Fedder,et al.  Entry of the POLAR spacecraft into the polar cusp under northward IMF conditions , 1998 .

[8]  T. Pulkkinen,et al.  Dispersive magnetosheath‐like ion injections in the evening sector on January 11, 1997 , 1998 .

[9]  Nikolai A. Tsyganenko,et al.  Effects of the solar wind conditions on the global magnetospheric configuration as deduced from data-based field models , 1996 .

[10]  J. Clemmons,et al.  Impulsive ion injections in the morning auroral region , 1995 .

[11]  M. Kivelson.  Pulsations and Magnetohydrodynamic Waves , 1995 .

[12]  T. Zawistowski,et al.  Hydra — A 3-dimensional electron and ion hot plasma instrument for the POLAR spacecraft of the GGS mission , 1995 .

[13]  D. Pierce,et al.  The GGS/POLAR magnetic fields investigation , 1995 .

[14]  Lou‐Chuang Lee,et al.  Kinetic Alfven waves as a source of plasma transport at the dayside magnetopause , 1994 .

[15]  T. Onsager,et al.  Model of magnetosheath plasma in the magnetosphere: Cusp and mantle particles at low‐altitudes , 1993 .

[16]  R. Lundin,et al.  Signatures of transient boundary layer processes observed with Viking , 1992 .

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

[18]  C. Russell,et al.  Observations of reconnection of interplanetary and lobe magnetic field lines at the high‐latitude magnetopause , 1991 .

[19]  T. Moore,et al.  A three‐dimensional numerical model of ionospheric plasma in the magnetosphere , 1989 .

[20]  R. Lundin.  On the magnetospheric boundary layer and solar wind energy transfer into the magnetosphere , 1988 .

[21]  S. Cowley.  The causes of convection in the Earth's magnetosphere: A review of developments during the IMS , 1982 .

[22]  I. Papamastorakis,et al.  Evidence for magnetic field reconnection at the Earth's magnetopause , 1981 .

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

[24]  R. Torbert,et al.  Solar wind ion injections in the morning auroral oval , 1980 .

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

[26]  I. Papamastorakis,et al.  Plasma acceleration at the Earth's magnetopause: evidence for reconnection , 1979, Nature.

[27]  J. Lemaire,et al.  Penetration of solar wind plasma elements into the magnetosphere , 1978 .

[28]  T. Hill,et al.  Solar wind plasma injection at the dayside magnetospheric cusp , 1977 .

[29]  E. Shelley,et al.  He ++ and H + Flux Measurements in the Day Side Cusp: Estimates of Convection El , 1976 .

[30]  S. Petrinec,et al.  Cusp observations of high- and low-latitude reconnection for northward interplanetary magnetic field , 2000 .

[31]  C. Russell,et al.  Solar wind control of the polar cusp at high altitude , 2000 .

[32]  T. Eastman,et al.  High-altitude cusp positions sampled by the Hawkeye satellite , 1997 .

[33]  R. Lundin,et al.  Temporal magnetoheath plasma injection observed with Viking: a case study , 1991 .