For personal research, I'm doing some analysis on collected data and trying to develop relationships between two variables where the data is collected through a data logger. I'm hypothesising that a = alpha * b for any point in my data logger.

Anyways I plotted the 5,000+ x,y points below, and the only relationship I see is a cloud or airplane wing shaped one where it is linear at the bottom and and a curved line on the top. Doing log scales didn't help either.

EDIT So I'm not allowed to submit image tags as a new user, but here's the graph

How can I improve my data analysis and is there a tool / cheat sheet that recommend a statistical analysis for a type of data.