A high-performance computing node is running two concurrent simulation packages for climate modeling: an atmospheric fluid dynamics model and an ocean temperature simulation.
The active memory requirement of these two concurrent simulations is 64 GB64\text{ GB}64 GB, but the computing node only has 32 GB32\text{ GB}32 GB of physical RAM installed.
Despite this memory deficit, both simulations continue to run concurrently without crashing.
Explain how the operating system uses virtual memory to manage this situation.