SENTRY Q & A: WHY IS THE SENTRY CAPABLE OF CALMING HULK DOWN?

As some of you might know the Sentry was capable of calming the Hulk down in the past and stopping his tantrums that way:

http://static.comicvine.com/uploads/original/11/116291/2178761-4.jpg

It was never really explained how he was able to do it, but there is a combination out of two reasons, which would make a lot of sense:

1. Sentry is capable of affecting the Hulk via empathy. 
When Void was mind-assaulting his opponents in the past he used it to confront them with everything bad from their past, present and future:

http://static.comicvine.com/uploads/original/11/116291/2178823-7.jpg

After being touched by the Void a person had an emotional breakdown and was in a state of shock afterwards.
Sentry has displayed it recently as well:

http://static.comicvine.com/uploads/original/10/108566/3511373-6.jpg

So his empathy can have a positive and a negative effect.

2. Hulk's state is directly being affected by a sub-part of Sentry's power set, which is the manipulation of solar radiation.
Sentry is capable of manipulating solar radiation in a way to turn himself invisible or shoot solar energy blasts, which he for example used to charge Iron Man's armor.

A little known fact about the Hulk is that his Hulk state is affected by the Sun:

http://static.comicvine.com/uploads/original/10/108566/3973451-hulkvssunvssentry.jpg

To sum it up... The more sunlight Hulk gets, the less malevolent the Hulk persona is. He wants to be left alone at that point and the Bruce Banner persona gains more control.
Sentry is capable of directly affecting the Hulk's rage with his solar radiation, simply by exposing him to more direct and concentrated sunlight.