We introduce here a simple method to calculate the Larmor radius of a charged particle in space, located in the Earth's vicinity. We calculate Earth magnetic field starting from particle posistion in the shifted tilted approximation as seen below.

Then Larmor radius is calculated with this simple formula

The rigidity is defined as

where p is the momentum, c is the speed of light, e is the electron charge, Z is the particle charge number, A is the mass number and kinetic and rest energy are per nucleon (if energy is in eV then rigidity is in Volts)

Last updated on 17-JUL-2002 by Davide Grandi