This document, authored by Donald H. Fairfield and published in December 1970, presents an analysis of the average and unusual locations of the Earth's magnetopause and bow shock based on data from six IMP spacecraft. The study aims to determine the average positions and variations of these boundaries, which are crucial for understanding the interaction between the solar wind and the Earth's magnetosphere. Key findings include: - The average geocentric distances to the magnetopause and bow shock near the ecliptic plane are 11.0 R_E and 14.6 R_E, respectively, in the sunward direction, and 15.1 R_E and 22.8 R_E in the dawn meridian, and 15.8 R_E and 27.6 R_E in the dusk meridian. - The bow shock hyperbola is oriented in a direction consistent with the expected radial solar wind. - Observed magnetopause crossings agree well with theoretical predictions in the noon meridian plane but fall outside the theoretical boundaries in the dawn-dusk meridian planes. - Solar wind momentum flux is the primary factor controlling the orbit-to-orbit changes in the boundary positions. - Interplanetary field orientation affects the distance to the magnetopause boundary, with more earthward crossings corresponding to southward fields. - Six unusual bow shock locations up to 22 R_E beyond the average position are attributed to an enhanced standoff distance associated with a low Alfven Mach number. - The possibility is raised that the solar wind may have become sub-Alfvenic on July 31, 1967. The analysis also discusses the asymmetry in the magnetopause and bow shock positions, the influence of geomagnetic activity, and the relationship between boundary positions and interplanetary magnetic field orientation. The study concludes that the solar wind momentum flux is the primary driver of boundary position variations, and that the effective ratio of specific heats (γ) is likely between 5/3 and 2 for the solar wind-earth interaction.This document, authored by Donald H. Fairfield and published in December 1970, presents an analysis of the average and unusual locations of the Earth's magnetopause and bow shock based on data from six IMP spacecraft. The study aims to determine the average positions and variations of these boundaries, which are crucial for understanding the interaction between the solar wind and the Earth's magnetosphere. Key findings include: - The average geocentric distances to the magnetopause and bow shock near the ecliptic plane are 11.0 R_E and 14.6 R_E, respectively, in the sunward direction, and 15.1 R_E and 22.8 R_E in the dawn meridian, and 15.8 R_E and 27.6 R_E in the dusk meridian. - The bow shock hyperbola is oriented in a direction consistent with the expected radial solar wind. - Observed magnetopause crossings agree well with theoretical predictions in the noon meridian plane but fall outside the theoretical boundaries in the dawn-dusk meridian planes. - Solar wind momentum flux is the primary factor controlling the orbit-to-orbit changes in the boundary positions. - Interplanetary field orientation affects the distance to the magnetopause boundary, with more earthward crossings corresponding to southward fields. - Six unusual bow shock locations up to 22 R_E beyond the average position are attributed to an enhanced standoff distance associated with a low Alfven Mach number. - The possibility is raised that the solar wind may have become sub-Alfvenic on July 31, 1967. The analysis also discusses the asymmetry in the magnetopause and bow shock positions, the influence of geomagnetic activity, and the relationship between boundary positions and interplanetary magnetic field orientation. The study concludes that the solar wind momentum flux is the primary driver of boundary position variations, and that the effective ratio of specific heats (γ) is likely between 5/3 and 2 for the solar wind-earth interaction.