
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
Given an ellipse $\dfrac {x^{2}}{a^{2}}+ \dfrac {y^{2}}{b^{2}}=1(a > b > 0)$, its left and right foci are $F_{1}$ and $F_{2}$, respectively, and its top vertex is $M$. If the slope of line $MF_{1}$ is $1$, and its other intersection point with the ellipse is $N$, and the perimeter of $\triangle F_{2}MN$ is $4 \sqrt {2}$.
$(1)$ Find the standard equation of the ellipse;
$(2)$ A line $l$ passing through point $F_{1}$ (the slope of line $l$ is not $1$) intersects the ellipse at points $P$ and $Q$, with point $P$ above point $Q$. If $S_{\triangle F_{1}NQ}= \dfrac {2}{3}S_{\triangle F_{1}MP}$, find the slope of line $l$.

Present the answer in LaTex format: \boxed{Your answer}
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