Bow shock and α component in the transition region, from measurements on the high-latitude satellite Prognoz

The times of intersection of the geomagnetospheric bow shock by the above satellite have been determined from measurements of the ion component of the plasma. We have determined the mean position of the shock for the period 4-15-to 9-17-1972, in the conic section approximation, and without allowing for the aberration angle. The distance of the shock at its flank was approximately 28.6 Earth radii, which is much larger than values from other experiments. A possible reason is that Prognoz intersected the shock at high latitudes. From measurements of the energy spectrum of α particles of the solar wind and in the transition region we have determined the temperature jump and the velocity of the α component of the plasma. The values obtained differ a great deal from values calculated from the gas dynamic flow model and from results of measurement of the proton component of the solar wind. At small angles (approximately 300) and at large angles (approximately 700) from the forward stagnation point the jump in the transition velocity of α particles is approximately 0.85 and the temperature jump is approximately 7, i.e., considerably less than for protons. Evidently, the α particle and proton transition velocities are not equal in the transition region. (author)