function kappa, vel, $ parameters=p ,units=units if not keyword_set(p) then $ p = {func:'kappa',n:10.0d,vh:2000.0d,k:6.0d,units:'df'} if n_params() eq 0 then return,p mass = 5.6856593e-06 a = 2./mass^2*1e5 vh2 = (p.k-1.5)*p.vh^2 c = (!dpi*vh2)^(-1.5) * gamma(p.k+1)/gamma(p.k-.5) ;energy = .5 * mass * total(vel*vel,2) energy = .5 * mass * vel*vel ;units = 'eflux' case p.units of 'df' : conv = c 'flux' : conv = c * a * energy 'eflux': conv = c * a * energy^2 endcase v2 = vel^2 f = p.n*conv*(1+(v2/vh2))^(-p.k-1) return,f end