Vela 3 Satellite Observations of Solar Wind Ions: A Preliminary Report
Abstract
The electrostatic analyzers on the Vela 3 satellites measure the ion flux with high resolution in both energy and direction. From the measured fluxes are computed values of the velocity distribution function at points on a plane in velocity space. The function is extended over the whole plane by interpolation and displayed by a contour mapping in this plane. From this mapping the properties of the function can be visualized, and parameters characterizing the ion component of the plasma can be computed. The distribution functions of solar wind protons observed during the first month the satellites were in orbit are found to be significantly anisotropic in a frame of reference moving with the local plasma bulk velocity. A ‘tail’ of protons with high random energies is usually present; evidence is presented that suggests that this tail is aligned with the interplanetary magnetic field lines, more often pointing away from the sun (along the lines) than toward the sun. The mean random energy or temperature of the protons is highest in this direction. The ratio of the maximum temperature to the average over-all directions ranges from 1.0 to about 2.5, with a value of 1.4 being most common. The existence of this anisotropy can be explained by the invariance of υ⊥²/B as the plasma expands from the sun. Similar anisotropic distribution functions are found for the He++ or α-particle component of the plasma. The ratio of number densities of the α's and protons is found to vary from 0.00 to 0.15, with a mean value of 0.042 during this period.
- Publication:
-
Journal of Geophysical Research
- Pub Date:
- January 1967
- DOI:
- 10.1029/JZ072i001p00087
- Bibcode:
- 1967JGR....72...87H