using CairoMakie
f = Figure(resolution = (400, 400))
Axis(f[1, 1], backgroundcolor = "black")
xs = LinRange(0, pi, 20)
ys = LinRange(0, 2pi, 20)
us = [2sin(x) * cos(y) for x in xs, y in ys]
vs = [-cos(x) * 2sin(y) for x in xs, y in ys]
strength = vec(sqrt.(us .^ 2 .+ vs .^ 2))
arrows!(xs, ys, us, vs, arrowsize = 10, lengthscale = 0.3,
arrowcolor = strength, linecolor = strength)
f