Experiments on wake structures behind a microparticle in a magnetized plasma flow

Abstract

This paper was selected as Featured ARTICLES YOU MAY BE INTERESTED IN Charging of an irregularly shaped particle in the sheath of an rf plasma

Transverse force induced by a magnetized wake

“…This shows that a significant influence of the magnetic field arises at β = 10, and that it smoothly transitions toward the β → ∞ limit as the magnetic field strength increases. For β = 10 4 , the full numerical solution closely approaches the β → ∞ limit, establishing that the simplified β → ∞ expression from equation (29) provides an accurate representation of the full linear response theory in the high magnetic field limit. With regard to the high magnetic field limit, recall that the expression for k max in equation (11) is made without reference to the magnetic field.…”

“…Qualitatively different behavior is observed in the strongly magnetized limit. This limit is indicated by the blue curves, which correspond to the solution of equations (19), (20) and (29). The magnitude of the force, as well as the position of the peak, is altered both parallel (F z ) and perpendicular (F x ) to the magnetic field, but in an asymmetric fashion with F x changing much more substantially than F z .…”

“…ζ ≡ M sgn(cos θ ) (cos θ + tan θ cos φ sin θ) , and D(ζ) is the Dawson function, which is related to the plasma dispersion function as Z(ζ) = −2D(ζ)+i √ π exp(−ζ 2 ). The components of the force in the strong magnetic field limit were computed by applying equation (29) in equations (19) and (20) and computing the angular integrals numerically.…”

“…One reason to focus on this limit is that it illustrates the basic physics processes associated with the influence of magnetization, with emphasis on the transverse force, in an extremum limit. It is also much less computationally expensive to solve equation (29) than to solve the full magnetized dielectric response function. This enables us to explore the phase dependence, wake potentials and trajectory calculations, which would be computationally difficult to do for an arbitrary magnetic field strength.…”

“…To emphasize the influence of the transverse force, the trajectory is computed both from the complete description and by arbitrarily setting the transverse force to zero (F × = 0). Both components of the friction force are computed using the β → ∞ description from equation (29). Figure 9 shows the trajectory of an initially supersonic particle (M = 2) at an angle of θ = 15 • with respect to the magnetic field in a background plasma with coupling strength Γ = 0.1.…”