Space between 2 scores

[Kamal]

I have the following:

\score {
{ c }
 \header {
   title = "Title1"
 }
 \layout {
   indent = 0.0
 }
}
\score {
{ c }
 \header {
   title = "Title2"
 }
 \layout {
   indent = 0.0
 }
}

\version "2.8.6"

What is the property which sets the vertical length between score1 &
score2 (indicated by a cross on the attached pic)?

I used:
\paper{
 printallheaders=##t
 annotate-spacing = ##t
}
But it show clearly what is the property name.

Lilypond 2.8.6