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)