Let $A$ be an abelian variety over a number field $K$ and consider the Neron model $\mathcal{A}$ of $A$ over $X=Spec{\mathcal{O}\_K}$. If $\mathcal{A}^0$ is the identity component of $\mathcal{A}$, then $\mathcal{A}^0$ is an open subgroup scheme of $\mathcal{A}$ that fits into a short exact sequence 
$$0 \rightarrow \mathcal{A}^0 \rightarrow \mathcal{A} \rightarrow \Phi\_A \rightarrow 0$$
over $X$. Considering these smooth group schemes as sheaves for the flat (fpqf) topology over $X$, the associated long exact sequence of flat cohomology groups begins
$$0\rightarrow\mathcal{A}^0(X)\rightarrow\mathcal{A}(X)\cong{A(K)}\rightarrow\Phi\_A(X)\rightarrow\ldots$$
where the indicated isomorphism follows from the Neron mapping property. Now, we know that $A(K)$ is finitely generated i.e. it has a free part (copies of $\mathbb{Z}$) and a torsion part (which is finite). Since $A(K)/{\mathcal{A}^0(X)}$ is contained within $\Phi\_A(X)$ (which is finite), it follows that the group $\mathcal{A}^0(X)$ of global sections of $\mathcal{A}^0$ must contain all of the free part of $A(K)$. My question is - is it possible in this general scenario to determine how much of the finite part of $A(K)$ is captured by $\mathcal{A}^0(X)$ or do we need additional information on $A$?



Global Sections of the Identity Component of Neron model
First, a remark: the free part of $A(K)$ is a quotient, not a sub, and so it is possible that a point of infinite order in $A(K)$ could have non-trivial image
in $\Phi\_A(X)$. Probably what you mean is that $\mathcal A^0(X)$ and $A(K)$ have the same
free rank. 


Regarding torsion, my interpretation of your question is that you are asking
about the map $A(K)\_{tors} \to \Phi\_A(X)$, and are curious is to whether or not it 
can have a kernel (so that some part of $A(K)\_{tors}$ is contained
in $\mathcal A^0(X)$). 


As far as I know, this varies a lot depending on the particular abelian variety,
but in particular cases it has been quite intensively studied. For example, if $p$
is prime and $A =J\_0(p)$ is the Jacobian of the modular curve $X\_0(p)$, then Mazur showed
in his Eisenstein ideal paper showed that the map $A(\mathbb Q)\_{tors} \to \Phi\_A(
\mathrm{Spec}\ \mathbb Z)$ is an isomorphism. I generalized this to subabelian varities
$A$ of $J\_0(p)$ in my paper [here](http://www.math.northwestern.edu/~emerton/pdffiles/optimal.pdf).


For an example in some sense opposite to this, see [this paper](http://math.stanford.edu/~conrad/papers/j1p.pdf) of Conrad, Edixhoven, and Stein,
in which they show that if $A = J\_1(p)$ (again $p$ is prime), then
$\Phi\_A(\mathrm{Spec}\ \mathbb Z)$ is trivial, so that $\mathcal A^0 = \mathcal A$.


