Subscript R notation for the finite fields I'm trying to understand the notation used in the literature for Pairing-based cryptography.
I know (and I hope I've understood it well) from Wikipedia that $\mathbb{Z}_p$ is the finite field of prime order $p$, where

$p$ is the order of the field
$q$ and the characteristic of the field and $q=p^n$

I came across this notation here and there while researching the Identity-Based Encryption (Boneh-Franklin): $$s \in_R\mathbb{Z}^*_q$$
The $\mathbb{Z}^*$ means that the finite field is provided with the multiplication operation.
But the $_R$ confuses me, as I can't find its meaning on the web.
Could somebody explain it?
PS: are the following notations equivalent? $GF(p)$, $\mathbb{Z}_p$, $\mathbb{Z}/p\mathbb{Z}$ and $\mathbb{F}_p$
To quote yyyyyyy from the comments:


  The $_R$ has nothing to do with the field — it is associated to $\in$!
  To quote your first link: "For a set $S$, by $a\in_R S$, we mean that
  $a$ is randomly chosen from $S$."


and to quote SEJPM from the comments:


  If $p\in \mathbb P$ (with $\mathbb P$ being the set of all primes)
  then the notations $GF(p);\mathbb Z_p;\mathbb Z/p\mathbb Z;\mathbb
 F_p$ are equivalent.