High Latitude MinimumTrap?

The high-latitude minimum can trap a bouncing particle, which then possesses a 2nd invariant
But will the ions stay in this region, bouncing forever, or drift away? Does the 3rd invariant also exist?
The literature didn’t say, but certainly minima exist on both sides of the cusp. We did a particle tracing simulation to investigate this possibility.

The high-latitude minimum can trap a bouncing particle, which then possesses a 2nd invariant