Empirical Model for the Earth's Cosmic Ray Shadow at 400 KM: Prohibited Cosmic Ray Access

摘要

It is possible to construct as unit sphere of access that describes the cosmic radiation allowed to an earth-orbiting spacecraft. In the upper hemisphere of the allowed portion of the cosmic ray sphere of access, the cosmic ray cutoffs can be ordered by application of Stormer theory in offset dipole coordinates. In the downward hemisphere, in westerly directions, the cosmic radiation is allowed at large zenith angles well below the spacecraft-earth horizon, with particles being able to reach satellites at 400 km altitude from large zenith angles of similar to 140 deg at azimuthal directions equatorward of west in both the northern and southern hemispheres. We have found it is possible to model the occluded portion of the cosmic ray sphere of access as a circular projection having a diameter bounded by the satellite-earth horizon. Maintaining tangency at the eastern each of the spacecraft-earth horizon, this optically occluded area is projected downward (toward the earth) by angle beta which is a function of the magnetic field inclination and cosmic ray arrival direction. This projected plane, corresponding to the forbidden area of cosmic ray access, is bounded by the spacecraft-earth horizon in easterly directions, and is rotated around the vertical axis by an angle alpha from the eastern direction, where the angle alpha is a function of the offset dipole latitude of the spacecraft. Keywords: Energetic particles; Satellite altitudes. (Author)