Asymptotic variation of elementary abelian p-extensions over P1

Let $A^d$ denote the coefficient space of all degree-d polynomials f in one variable for some $d\ge 3$. For any $\bar{f}\in A^d\left({\bar{F}}_p\right)$, a rank-ℓ Artin-Schreier curve $X_{\bar{f},\ell }:y^{p^{\ell }}-y=\bar{f}$ is called ordinary if its normalized Newton polygon achieves the infimum in $A^d\left({\bar{F}}_p\right)$. Given ℓ and a number field K, we show that there exists a Zariski dense open subset $U$ in $A^d$, defined over $Q$, such that if $f\in U\left(K\right)$ then $X_{(f\mathrm{mod}\wp ),\ell }$ is ordinary for all primes $\wp |p$ with $\mathrm{deg}(\wp )\in \ell Z$ and p large enough.