The answer is: movement of otoliths along hair cells
Sense of static equilibrium refers to the way we interpret our current head position. This sense is extremely important for us to maintain our balance and posture.
When we move our head, it would create a movement of the otoliths along the hair cells. Based on this movement, the otoliths would send a signal to our central nervous system regarding the position of our head so it can help us maintain our balance.