Transverse Force Induced by a Magnetized Wake

TL;DR

This paper calculates the transverse force on a test charge in a strongly magnetized plasma, revealing an asymmetry in the electrostatic wake potential caused by the magnetic field, which affects particle trajectories without changing energy.

Contribution

It introduces a novel analysis of the transverse force induced by strong magnetization, highlighting its dependence on particle speed and its impact on particle trajectories.

Findings

Transverse force depends on test charge speed relative to a critical sound speed.

The force alters particle trajectories significantly over Coulomb collision times.

The force does not directly change the test charge's total energy.

Abstract

The force on a test charge moving through a strongly magnetized plasma is calculated using linear response theory. Strong magnetization is found to generate a component of the force perpendicular to the velocity of the particle in the plane formed by the velocity and magnetic field vectors. This transverse force is generated by an asymmetry with respect to the velocity vector in the induced electrostatic wake potential that is associated with the action of the Lorentz force on the background plasma. The direction depends on the speed of the test charge. If it is faster than a critical speed characteristic of the sound speed, it acts to reduce the component of velocity parallel to the magnetic field and to increase the gyroradius. In contrast, if the speed is below this critical speed, it acts to increase the velocity parallel to the magnetic field and to decrease the gyroradius. Because the transverse force is perpendicular to the velocity, it does not directly influence the total energy of the test charge. Nevertheless, it significantly alters the trajectory on a timescale associated with the Coulomb collision time.