# What is the name for this distribution defined on a circle

One can define the probability distribution: $$p(\theta; \alpha, \theta_0) = \frac{ e^{ \alpha \cos( \theta-\theta_0) }}{ 2 \pi I_0(\alpha)}$$ over an angular variable $\theta \in [0,2 \pi]$. By what name(s) is this distribution called?

($I_0$ is the modified Bessel function and serves to normalize the distribution)

For reference, $I_0(z)$ is the modified Bessel function of order 0.