PSE randomly goes up or down by 1 level when defeating enemies. Clearing a trial while at PSE level 4 triggers a PSE Burst.
Defeating enemies within the E marker has no effect on how frequently PSE levels up, but has a very slight and almost unnoticeable effect on how often it goes down.
The E marker will move when the majority of enemies in the current E marker are defeated. Enemy size and difficulty have no effect on when it moves.
Defeating enemies is how you cause Trials to appear.
Thunderstorm, Sandstorm, and Snowstorm weather cause PSE to be locked in at level 4 for their duration.
If a PSE Burst has not occured for five minutes for the oldest player in the room, then PSE level can no longer go down. This timer resets upon this player changing.
Passage of otherwise time has no effect on PSE. The level will not change outside of enemies being defeated or a Storm occuring.
A PSE Burst will spawn enemies and respawn them immediately upon defeat for a set duration of time. There is a cap on enemies that can spawn, but it is high.