Ion cyclotron modes excited in a low density, cylindrical plasma cavity using an external inductive antenna are investigated theoretically and experimentally. These modes, which have a long parallel wavelength, exhibit a strong electrostatic character and are only weakly coupled to the antenna fields. Comparison is made of the measured wavefields with those predicted by a theory that includes the influence of electron dynamics. It is thus shown that not only the electron inertia but also electron Landau damping plays an important role in determining the cavity mode structure.