... A plasma instability involves plasma waves that grow exponentially or faster. For proper discription of a particular instability, one should be able to define . the mode of the growing wave . ... Other familiar examples are the Rayleigh-Jeans instability, in which a denser fluid is supported by a less dense fluid, and the Kelvin- Helmholtz instability , in which one fluid flows over another fluid, e.g., wind over water, causing surface waves to grow. ... Ballooning mode instability . ...