I'm trying to make a StreamPlot in Mathematica with three variables. I already have two variables, x and y, that make an ellipse via

StreamPlot[{-y,x}]

but I want the vectors to increase as you move radially out from the center (ie ideally I would want a third variable, v, so that it looked like

StreamPlot[{-vy, vx}]

So that as v increased the vectors increased as well.

I'm trying to make a StreamPlot in Mathematica with three variables. I already have two variables, x and y, that make an ellipse via

StreamPlot[{-y,x}] 

but I want the vectors to increase as you move radially out from the center (ie ideally I would want a third variable, v, so that it looked like

StreamPlot[{-v*y, v*x}] 

So that as v increased the vectors increased as well.