lucubration \loo-kyoo-BRAY-shun; loo-kuh-\, noun:
1. The act of studying by candlelight; nocturnal study; meditation.
2. That which is composed by night; that which is produced by meditation in retirement; hence (loosely) any literary composition.

About a third of my writing is done in the dark. Well at least at night if not actually in the dark. I discovered years ago that what I produce in the wee hours is of a different quality than my work product in the bright of day.

Sheer numbers tell me that I produce a lot more words on the page when writing during the day but they are of a very different flavor than my night writing. The emotive content, the big twists and turns come at night. Moving the story along filling in the linear details is a daytime activity.

Nocturnal work also contains a lot of marginalia both on previous sections and notes for future writing. There are times when the fingers just can't keep up with the ideas so I take lots of notes. This nearly always happens at night. 

A new day of writing generally begins with reading yesterday's work. Words produced after dark often require a fair amount of daylight editing if only to fill in all the linkages for a potential audience. It's not stream of consciousness writing, well most of the time it isn't but methinks the collective unconsciousness rises closer to my waking world when the sun is on the far side of Gaia.