Vela Satellite Measurements of Particles in the Solar Wind and the Distant Geomagnetosphere

211

116

The Explorer 33 satellite was launched July 1, 1966 and was injected into a highly elliptical earth orbit. The Goddard Space Flight Center magnetic field experiment onboard the spacecraft consists of a triaxial fluxgate sensor with a maximum dynamic range of ±64 gammas and a sensitivity of ±0.25 gamma along each axis. Because of the initial apogee‐earth‐sun angle of 118° west of the sun, the first 8 orbits of Explorer 33 (July 1 to November 11, 1966) mapped the earth's magnetosheath and magnetic tail from the western flank of the bow shock to the eastern flank. This mapping of the geomagnetic tail out to 80 earth radii established that the tail extends beyond the lunar orbital distance. Explorer 33 has also found that the earth's bow shock is still a detectable boundary between the interplanetary magnetic field and the downstream magnetosheath at a geocentric distance of 75.7 earth radii. The measurements have further suggested that the cross section of the geomagnetic tail is probably not cylindrical and have shown that the magnetic field magnitude in the tail decreases with distance down the tail from the earth.

Section: Historical Backgroundmentioning

confidence: 82%

Mapping of the Earth's bow shock and magnetic tail by Explorer 33

Behannon¹

1968

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116

“…It is evident that measurements of the solar wind during geomagnetic storms are needed for a complete understanding of these storms and related phenomena. In this regard, Mariner 2 measurements reported by Snyder et al [1963] and Vela 2 measurements reported by Strong et al [1965] and Coon [1966]…”

Section: Introductionmentioning

confidence: 90%

Measurements of the interplanetary solar wind during the large geomagnetic storm of April 17-18, 1965

Gosling¹,

Asbridge²,

Bame³

et al. 1967

During the large geomagnetic storm of April 17–18, 1965, measurements of the solar wind were made with electrostatic analyzers on the Vela 2 satellites. A number of the observed solar wind changes can be related to worldwide geomagnetic changes; the most impressive event occurred after the main phase development when a fivefold increase in the solar wind density resulted in a sudden geomagnetic impulse. During the initial phase of the storm the plasma measurements were not complete, but the evidence indicates that the wind pressure increased at the time of the sudden commencement, and other features of the initial phase seem to have been related to solar wind changes. However, the main phase of the storm developed during a period when the solar wind remained relatively steady; further, there was nothing abnormal about the magnitude of the velocity, temperature, or proton density at that time. The α‐particle flux during this period was higher than usual. The storm recovery was characterized by a period of rising solar wind velocity and temperature.

“…The pitch angle distribution of the energetic electrons when they appear is not known from the present measurements. However, some results from the Vela satellite measurements [Coon, 1965] suggest that these fluxes may be more or less isotropic. In that case s-• --• 1, and the partial pressures, p -sin a R, found from Table 2 lie mostly in the range 0.5 to 1.7%.…”

Section: Gives the Z•• Coordinate At The Boundaries Of The Depressiomentioning

confidence: 99%

Correlation of magnetic fields and energetic electrons on the IMP 1 satellite

Anderson

Ness

1966

A study of simultaneous magnetic field and energetic particle records from the IMP 1 satellite on the dark side of the earth has shown several distinct correlations that can be understood as diamagnetic effects of charged particle populations. Depression of the magnetic field in the closed magnetic field line configuration of the particle cusp region is observed on most orbits. A small but significant portion of this effect can be attributed to the diamagnetic effects of electrons >45 kev. In the geomagnetic tail region, large depressions of the magnetic field having radial extent ∼10 RE are observed when the satellite approaches the neutral sheet to within ∼5 RE. Energetic electron fluxes appear throughout this volume and show no strong preference to occur immediately adjacent to the neutral sheet. In this region, less than 1% of the diamagnetic effect is due to electrons >45 kev. Finally, there are examples of intense, energetic electron fluxes closely associated with reduction of the magnetic field magnitude. In one case, an electron flux of 3×106 cm−2 sec−1 >45 kev was associated with a field change from 20 γ to 8 γ.