If we wanted to take account of the tendency for the neutral sheet to approach the magnetospheric equator, we would multiply the right hand side of equation 1 by a function of the distance of the point of observation behind the earth. Two sets of data on the positions of the neutral sheet have been reported up to this date. This arbitrary cutoff in X was chosen since the errors involved are possibly greater than 3 o and the plotting of these points in Figures 1 and 2 requires a division by sin . In addition several crossings found in the OGO 1 data have been omitted because of insufficient data coverage either before or after the crossing. The distance above the magnetospheric equator normalized by dividing by the sine of the magnetic latitude of the subsolar point plotted versus the magnetospheric Y coordinate for neutral sheet crossings observed by IMP 1 and OGO 1.
Distances are in earth radii.
This plot is equivalent to normalizing the position of the observed crossings to the equivalent position if the dipole axis were aligned with the solar wind. If equation 1 holds, i.e. there is no X dependence, and the neutral sheet starts from a circle in the geomagnetic equator, then within the errors mentioned above we expect the points to fall on a circle. If the neutral sheet started from an ellipse in the geomagnetic equator, the points would fall on an ellipse in this plot. Within the scatter of the data shown here a circle fits just as well as an ellipse. Although a strictly circular shape would not be expected physically, the spread in the data does not justify a more complicated approximation than a circle.