We have noted that the Bohm criterion requires the ions to enter the Debye sheath at the sound speed.

Once the ions enter the region between the electrodes, they are accelerated towards the center.

If the ions are entering the sheath too slowly, the sheath potential will "eat" its way into the plasma to accelerate them.

The Bohm criterion requires the ions to enter the Debye sheath at the sound speed.

These ions enter a water supply by leaching from minerals within an aquifer.

Because while ions can enter the pores, they cannot leave since they are not volatile.

Importantly, they exit from a spot right behind where the ion entered.

The positive ions then enter the cell following concentration and electrical charge gradient and propagate to the rest of the neuron.

Most water and ions enter the lake directly from precipitation or snow-melt.

The dissolved ions enter the blood stream (a water-based solution) and encounter a cell membrane.