Evidence for drift waves in ionospheric heating experiments

Universal Drift Wave instabilities commonly occur in laboratory plasmas and yet have not been detected in space experiments. Meter‐scale waves occurring in convective ionospheric storms, also known as equatorial spread F conditions, were long thought, erroneously, to be caused by drift waves, even though laboratory simulations of the Rayleigh‐Taylor instability seem to result in drift modes. Most space‐based instabilities occur at such large scales that the gradients required to support drift waves are simply too weak. The results of a laboratory‐like experiment, performed in space using high power radiowaves, are then revisited. Such experiments produce modest density depletions having very short scales across the magnetic field. Here, wavelets are used to parse the signal into a deterministic structure—the needle‐like irregularities—and a noise‐like signal corresponding to waves trapped in the depletions, which are very likely lower hybrid drift waves. Recent space experiments have revealed natural phenomena with similar characteristics.