Effect of Altitude on the Position of the Magnetic Pole

Abstract

IN the most recent analysis of the Earth's magnetic field (for the epoch 1942), Spencer Jones and Melotte¹ evaluated forty-eight coefficients in the spherical harmonic expansion of the magnetic potential. Using their values for a spheroidal Earth, the X (northerly) and Y (easterly) components of the Earth's magnetic field were calculated at heights of 100 km. and 250 km. above the Earth's surface for θ = 5°, 10°, 15°, 20° and 25° and for ϕ = 240°, 250° and 260° E., where θ and ϕ are the co-latitude and longitude respectively. The heights 100 and 250 km. were chosen to correspond to the E- and F-layers of the ionosphere. For the purpose of comparison, X and Y were also evaluated at the Earth's surface and in every case the value of H = (X ² + Y ²)^1,2 was computed.