galpy.potential.planarPotential.phiforce

planarPotential.phiforce(R, phi=0.0, t=0.0)[source]

NAME:

phiforce

PURPOSE:

evaluate the phi force = - d Phi / d phi (note that this is a torque, not a force!)

INPUT:

R - Cylindrical radius (can be Quantity)

phi= azimuth (optional; can be Quantity)

t= time (optional; can be Quantity)

OUTPUT:

F_phi(R,(phi,t)))

HISTORY:

2010-07-13 - Written - Bovy (NYU)