Ponderomotive redistribution of heavy ions along a magnetic field line

Abstract

We set up the problem of ponderomotive separation and acceleration of ions with different charge-to-mass ratios under the influence of Alfvén waves, which constantly exist in the magnetosphere in the form of geomagnetic pulsations. Formulas for partial ponderomotive forces acting on light and heavy (metallic) ions are derived. In the quasi-hydrodynamic approximation, a system of equations is obtained which describes the distribution of ions along magnetic field lines in Earth’s magnetosphere. The Clarke number, which characterizes plasma metallicity, is found to be maximum at a minimum magnetic field on the field line along which the Alfvén wave propagates. This leads to the accumulation of heavy ions at the top of the field line at the point of its intersection with the magnetic equator. The theoretical conclusions agree with satellite measurements of the distribution of heavy ions along field lines in Earth’s magnetosphere.

Keywords

• partial ponderomotive forces
• alfvén waves
• heavy ions
• ambipolar diffusion
• geomagnetic field
• clarke number