ON SPURIOUS MODES DOR FINITE LARMOR RADIUS MODELS IN THE ION-CYCLOTRON RANGE OF FREQUENCIES

Spurious resonances exist in the dispersion relations for finite Larmor radius models in plasma heating in the ion cyclotron range of frequencies. The spurious resonances occur when the highest-order coefficient in a fourth-order equation vanishes. It is shown that the spurious resonances cannot be removed by using a sixth-order equation because the highest-order coefficient in the sixth-order equation also vanishes at the same location as the highest-order coefficient in the fourth-order equation. However, the spurious modes are often not excited when solving the corresponding ordinary differential equations (ODEs) for an incident fast wave so that the solutions from the ODEs are often accurate. © 1995 American Institute of Physics.