  In this article, we give, under the Riemann hypothesis, an upper bound for
the exponential moments of the imaginary part of the logarithm of the Riemann
zeta function on the critical line. Our result, which gives information on the
fluctuations of the distribution of the zeros of $\zeta$, has the same accuracy
as the result obtained by Soundararajan in his paper entitled "Moments of the
Riemann zeta function".
