Analytic solution to the dynamical friction acting on circularly moving perturbers

Understand

We present an analytic approach to the dynamical friction (DF) acting on a circularly moving point mass perturber in a gaseous medium.

• We demonstrate that, when the perturber is turned on at $t=0$, steady-state (infinite time perturbation) is achieved after exactly one sound-crossing time.
• At low Mach number $\mathcal{M}~\ll~1$, the circular-motion steady-state DF converges to the linear-motion, finite time perturbation expression.
• The analytic results describe both the radial and tangential forces on the perturbers caused by the backreaction of the wake propagating in the medium.