Pressure Balance between Solar Wind and Magnetosphere

An evaluation of the subsolar pressure balance between the solar wind and the geomagnetic field shows that the average proton density of the quiet-day solar wind (300-400 km/sec) should be between 6 and 10 p/cm a. Even during storm times the proton density should always be between 2 p/cm 3 and 70 p/cm 3. The relation between the interplanetary solar-wind parameters and the stagnation pressure is reviewed. The subsolar geomagnetic field, including the quiet-day ring current field, is evaluated as a function of subsolar distance. The quiet-day ring current is based on the dipole gradient-drift motion of the low-energy protons observed by Davis and Williamson and by Frank. This quiet-day ring current has a magnetic moment of 0,?6 MB and produces a 41-? decrease at the earth's surface. A geomagnetic field normalization of observed boundary distances is also proposed to remove the effects of the dipole tilt to the solar wind.