已知曲线\(C:\begin{cases} & x=2\cos a \\ & y=\sqrt{3}\sin a \end{cases}(a\)为参数\()\)和定点\(A(0,\sqrt{3})\),\({F}_{1},{F}_{2} \)是此曲线的左、右焦点,以原点\(o\)为极点,以\(x\)轴正半轴为极轴,建立极坐标系.
\((1)\)求直线\(A{{F}_{2}}\)的极坐标方程;
\((2)\)经过点\({{F}_{1}}\)且与直线\(A{{F}_{2}}\)垂直的直线交此圆锥曲线于\(M,N\)两点,求\(\left| \left| M\left. {{F}_{1}} \right|-\left| N{{F}_{^{1}}} \right. \right| \right|\)的值.