Class that implements a steady-state spiral potential
V(r,phi,t) = A/alpha cos(alpha ln(r) - m(phi - Omegas*t-gamma))
NAME:
__init__
PURPOSE:
initialize a logarithmic spiral potential
INPUT:
amp - amplitude to be applied to the potential (default: 1., A below)
gamma - angle between sun-GC line and the line connecting the peak of the spiral pattern at the Solar radius (in rad; default=45 degree)
A - force amplitude (alpha*potential-amplitude; default=0.035)
omegas= - pattern speed (default=0.65)
m= number of arms
Either provide:
- alpha=
- p= pitch angle (rad)
tform - start of spiral growth / spiral period (default: -Infinity)
tsteady - time from tform at which the spiral is fully grown / spiral period (default: tform+2 periods)
OUTPUT:
(none)
HISTORY:
2011-03-27 - Started - Bovy (NYU)