Observation of the Coupled Mode of a Collisional Drift Wave and an Alfvén Wave

We observe a low-frequency instability with $\omega \ll {\omega }_{\mathrm{ci}}$ in a steady high-density plasma ($n_0\simeq {10}^{13-14}$ ${\mathrm{cm}}^{-3\mathrm{}}$). This instability has components of magnetic field fluctuations as well as density fluctuations. By introducing the dispersion relation, the instability is interpreted as the coupled mode of the collisional drift wave and the Alfvén wave.