  We investigate some aspects of the $m$-division field $K({\mathcal{E}}[m])$,
where $\mathcal{E}$ is an elliptic curve defined over a field $K$ with
${\textrm{char}}(K)\neq 2,3$ and $m$ is a positive integer. When $m=p^r$, with
$p\geq 5$ a prime and $r$ a positive integer, we prove
$K(\mathcal{E}[p^r])=K(x_1,\zeta_p,y_2)$, where $\{(x_1, y_1),(x_2,y_2)\}$ is a
generating system of ${\mathcal{E}}[p^r]$ and $\zeta_p$ is a primitive $p$-th
root of the unity. If $\mathcal{E}$ has a $K$-rational point of order $p$, then
$K(\mathcal{E}[p^r])=K(\zeta_{p^r},\sqrt[m_1]{a})$, with $a\in K(\zeta_{p^r})$
and $m_1|p^r$. In addition, when $K$ is a number field, we produce an upper
bound to the logarithmic height of the discriminant of the extension
$K(\mathcal{E}[m])/K$, for all $m\geq 3$. As a consequence, we give an explicit
effective version of the hypotheses of the local-global divisibility problem in
elliptic curves over number fields.
