Add more distribution setup

[henry2004y]

Besides Maxwellian, we want to add other analytical distributions functions:

• Bi-Maxwellian
• Kappa distribution
• Self-similar distribution

[henry2004y]

using PyPlot

fm(v) = exp(-v^2)
fk(v, κ) = (1+v^2/κ)^(-κ)

κ = [2, 5, 10, 20]
xrange = range(-4.75, 4.75, 100)

semilogy(xrange, fm.(xrange), "k--", label="Maxwellian")
for i in eachindex(κ) 
    semilogy(xrange, fk.(xrange, κ[i]), label="κ = $(κ[i])")
end

ylim(1e-4, 1)

legend()
savefig("kappa_distributions.png", bbox_inches="tight")

[henry2004y]

Actually the above one is a simplified version of the Kappa distribution. Check this paper for the full version.