A flood of emotions?

What is a word to describe a flood of positive emotions when confronted with a trigger from a past experience?

"A wave of nostalgia"

The madeleine effect?

Inspired by Marcel Proust and the 'petite madeleine' cookie:

Involuntary memory, a subcomponent of memory that occurs when cues encountered in everyday life evoke recollections of the past without conscious effort.

Reference:
https://en.wikipedia.org/wiki/Involuntary_memory

Erm possibly a blast from the past?

a blast from the past
Someone or something that evokes a sense of nostalgia. Bumping into my old high school sweetheart in the grocery store was a real blast from the past. Wow, I used to have this baseball card when I was kid. What a blast from the past!

Reference:
http://idioms.thefreedictionary.com/a+blast+from+the+past

A bit more about the origin:
http://www.phrases.org.uk/meanings/66500.html

There are probably several terms you can borrow from Marcel Proust's Remembrance of Things Past:

She sent out for one of those short, plump little cakes called 'petites madeleines,' which look as though they had been moulded in the fluted scallop of a pilgrim's shell. And soon, mechanically, weary after a dull day with the prospect of a depressing morrow, I raised to my lips a spoonful of the tea in which I had soaked a morsel of the cake. No sooner had the warm liquid, and the crumbs with it, touched my palate, a shudder ran through my whole body, and I stopped, intent upon the extraordinary changes that were taking place. An exquisite pleasure had invaded my senses, but individual, detached, with no suggestion of its origin. And at once the vicissitudes of life had become indifferent to me, its disasters innocuous, its brevity illusory--this new sensation having had on me the effect which love has of filling me with a precious essence; or rather this essence was not in me, it was myself. I had ceased now to feel mediocre, accidental, mortal. Whence could it have come to me, this all-powerful joy? I was conscious that it was connected with the taste of tea and cake, but that it infinitely transcended those savours, could not, indeed, be of the same nature as theirs. Whence did it come? What did it signify? How could I seize upon and define it?