Let us consider the imaginary parts of the Riemann Zeta function non-trivial zeros $\rho _{n}$.

Let us now consider the following sum:
$\tau (n)=\sum_{1}^{n}\sin(n)\sin(\rho _{n})$

This is the plot of $\tau (n)$ for $n$ between 1 and $10^4$:
[Plot 1][1]

My question is: does anyone know any articles where this periodicity is investigated?

  [1]: https://i.sstatic.net/xqpws.png