Secular Magnetic Variation and the Inner Zone.

The secular variation of the earths magnetic field has important consequences concerning the steady-state inner zone of energetic protons. One consequence is the decrease in minimum altitude for particles having a constant flux invariant Phi and a constant invariant parameter Kappa. This affects the rate at which particles lose energy to free and bound atmospheric electrons. Another consequence is the increase in the magnitude of the mirror-point field, resulting in a slow increase in a particles energy. It is found that for equatorially mirroring particles at a nominal L 1.10, conservation of Kappa and Phi causes the minimum mirror altitude to decrease at a rate of 6 kmyear using the IGRF 1965.0 model for the earths magnetic field, and at a rate of 11 kmyear using the POGO 869 model. Author