Examining the following graph, I am trying to understand the power plot. The power appears to take on a negative value when the current changes direction or the voltage changes polarity. Negative power does not make sense to me. In a proper representation of the power curve shouldn't the power remain above the dotted line?
Additionally, since the power is a product of voltage and current, I would think that the power plot should be a maximum value during where the plots of the voltage and current intersect, and should be greater in magnitude the the plots of the voltage and current.

![enter image description here](https://i.stack.imgur.com/CalKa.png)