Relation between geomagnetic sudden impulses and solar wind pressure changes-An experimental investigation

Theoretically the relation between the size of a geomagnetic sudden impulse si and the associated change in the solar wind stagnation pressure Ps is given by where (1) and (2) refer to pressures before and after the event and k is a proportionality constant. We have determined k experimentally using the M.I.T. solar wind measurements on Pioneer 6. The results support the general functional relation given above; however, the experimental value for k is approximately ½ that expected theoretically. This discrepancy was also found in a direct comparison of geomagnetic field strength and different solar wind pressures on quiet days. Several factors might contribute to the difference, such as the seasonal inclination of the dipole axis, the solar wind magnetic field, and the magnetospheric particle population.