Observations of the internal structure of the magnetopause

Magnetic field, plasma flux, and ELF wave data have been studied for several encounters of Ogo 5 with the earth's magnetopause. In one case of a crossing in the near-earth region of the geomagnetic tail, the structure agreed closely with a simple Chapman-Ferraro type of model with nearly complete neutralization of the charge separation electric field. The proton turning region was 4 times thicker than the electron turning region. The magnetic pressure was linearly related to the ion flux throughout most of the structure; this relation implies that pressure balance was maintained principally by a variation of proton number density across much of the field strength gradient. The computed gas dynamic constant of 0.77 ± 0.23 is in agreement with the value of 0.83 predicted for such cases of aligned flow. This linear relation between B² and ion flux was not observed at all of the crossings studied. Other departures from the simple structure were observed at other magnetopause crossings: (1) Field strength bumps were sometimes observed just earthward of the ion flux gradients on nontail field lines at which the field underwent a large rotation at the magnetopause. These interior maximums may be a diamagnetic effect due to the loss of trapped particles within one gyrodiameter of the magnetopause. The interior bumps were accompanied by exterior dips or local minimums in field strength. (2) One crossing revealed a well-defined double structure with a large change in field direction closer to the earth than the ion flux and field strength gradients. (3) The thickness of the magnetopause often depended on whether the change in field strength, the change in field direction, or the change in ion flux was being considered. (4) Bursts of ELF waves were occasionally observed at the magnetopause. Although some of these emissions resembled the ‘lion roars’ often observed in the magnetosheath, other magnetopause emissions had spectra unlike the spectra of bursts observed in either the magnetosphere or the magnetosheath.

[1]  R. Kaufmann,et al.  Speed and thickness of the magnetopause , 1973 .

[2]  G. Siscoe,et al.  Magnetopause motions at lunar distance determined from the Explorer 35 Plasma Experiment , 1972 .

[3]  J. Wolfe,et al.  Evidence of a diffuse magnetopause boundary , 1972 .

[4]  D. Willis.  Structure of the magnetopause , 1971 .

[5]  B. Sonnerup.  Magnetopause structure during the magnetic storm of September 24, 1961 , 1971 .

[6]  B. Ledley.  Magnetopause attitudes during Ogo 5 crossings , 1971 .

[7]  B. Sonnerup,et al.  On the equilibrium of the magnetopause current layer , 1971 .

[8]  J. Scudder,et al.  Magnetic field and electron observations near the dawn magnetopause , 1971 .

[9]  C. Russell,et al.  Motion and structure of the magnetopause , 1971 .

[10]  Christopher T. Russell,et al.  Inward motion of the magnetopause before a substorm , 1970 .

[11]  W. Feldman,et al.  Pressure balance across the distant magnetopause , 1970 .

[12]  E. Karlson.  On the equilibrium of the magnetopause , 1970 .

[13]  M. Neugebauer.  Initial deceleration of solar wind positive ions in the Earth's bow shock , 1970 .

[14]  A. Hundhausen,et al.  Plasma flow pattern in the Earth's magnetosheath , 1969 .

[15]  Edward J. Smith,et al.  Magnetic emissions in the magnetosheath at frequencies near 100 Hz , 1969 .

[16]  E. Smith,et al.  OGO Search Coil Magnetometer Experiments , 1969 .

[17]  C. M. Davies.  The boundary layer between a cold plasma and a confined magnetic field when the plasma is not normally incident on the boundary , 1968 .

[18]  P. Coleman,et al.  Magnetic fields in the magnetopause and vicinity at synchronous altitude , 1968 .

[19]  R. Wolf,et al.  TRANSFER PROCESSES IN THE MAGNETOPAUSE. , 1968 .

[20]  A. Hundhausen,et al.  SOLAR WIND ELECTRONS: VELA 4 MEASUREMENTS. , 1968 .

[21]  V. Ferraro,et al.  Discussion of paper by E. N. Parker, ''Confinement of a magnetic field by a beam of ions.'' , 1968 .

[22]  L. J. Cahill,et al.  Explorer 12 observations of the magnetopause current layer , 1968 .

[23]  I. Lerche.  On the boundary layer between a warm, streaming plasma and a confined magnetic field. , 1967 .

[24]  T. Skillman,et al.  OGO-A magnetic field observations , 1967 .

[25]  C. Russell,et al.  Magnetic Noise in the Magnetosheath in the Frequency , 1967 .

[26]  E. Parker.  Small-scale nonequilibrium of the magnetopause and its consequences. , 1967 .

[27]  L. J. Cahill,et al.  The boundary of the geomagnetic field, August to November, 1961 , 1967 .

[28]  E. Parker.  Confinement of a magnetic field by a beam of ions. , 1967 .

[29]  L. J. Cahill,et al.  Magnetopause structure and attitude from Explorer 12 observations. , 1967 .

[30]  G. Siscoe,et al.  Magnetic fluctuations in the magnetosheath - Mariner 4. , 1967 .

[31]  F. Vescelus,et al.  OGO-E plasma spectrometer. , 1967 .

[32]  R. Snare,et al.  A Magnetic Field Instrunent for the OGO-E Spacecraft , 1966 .

[33]  A. Summers,et al.  Hydromagnetic flow around the magnetosphere , 1966 .

[34]  E. Smith,et al.  Preliminary results from the Ogo 1 Search Coil Magnetometer: Boundary positions and magnetic noise spectra , 1966 .

[35]  L. Lees.  Interaction between the solar plasma wind and the geomagnetic cavity , 1964 .