How do I set the scroll bar of a div on top?

How do I set the scroll bar of a div on top?

I have a div with a long text, it shows the vertical scroll bar. I
show-hide this div with Jquery so it looks like a popup.
When it's hidden the scroll remains at the place the user put it, so when
it shows up againg the scroll is at the same place, I want it to be on top
every time it shows up again.
So the question is: How do I set the scroll bar of a div on top with jquery??
CODE:
<div class="scroll_div" align="justify">
<p align="center">
Text text text text text text text text text
text text text text text text text text text
text text text text text text text text text
.............
.............
</p>
</div>