Plasma instabilities due to ion temperature gradients

The dispersion relation for an inhomogeneous, low-pressure, collisionless magnetized plasma with ion temperature gradients is solved numerically in the regime where the plasma dispersion function cannot be expanded in a power series. The plasma is found to be unstable to low frequency, electrostatic perturbation at least in the range , 0.2 ⪅ T e /T i lap; 5, ω ⪅ k ‖ v i , and possibly for a wider range of parameters (where r i as the ion Larmor radius, T the temperature, v i the ion thermal velocity, k⃗ the wave vector). It is believed that the magneto-ionic acoustic waves observed in a thermal potassium plasma are manifestations of such instabilities. Additional experimental evidence is given in support of this assertion.