coordinates of their radius vectors? The cusps are due to the interaction of the Earth's magnetic field and the magnetic field imbedded in the solar wind. They move around as the Earth moves around the Sun and as the tilt of the Earth's axis moves. They also move in position, as well as distance from the Earth, as the magnetic field of the Sun changes. So they don't point at any fixed direction. I am working on a paper on the interaction of the solar wind with the Earth's magnetosphere. Do you know of a source giving the magnitude of the magnetic field of the magnetosphere? Your question has a tremendous amount of latitude in it, both literally and figuratively. The magnitude of the Earth's magnetic field within the magnetosphere varies greatly with location within the magnetosphere. It is not a simple question to answer. The magnetosphere is formed when the flow of the solar wind impacts the Earth's magnetic field (a dipole field), compressing it, causing magnetic reconnection, causing complex currents to flow, etc. The dipole field changes greatly under the influence of the solar wind. Try to get a copy of "Physics of the Magnetopause" published by the AGU. That will help. The magnetic field in the solar wind near Earth is about 5 nT, or 5 x 10(-5) Gauss. The magnetic field on the surface of the Earth is about 0.5 Gauss - big difference. If you were to imagine a spacecraft passing from the solar wind