Observation of Bound States and Counterrotating Lower Hybrid Eigenmodes in the Auroral Ionosphere

Definitive evidence from a plasma wave interferometer carried on a sounding rocket is presented for the observation of counterrotating electric field structures observed at frequencies above and below the local lower hybrid resonance frequency, $f_{\mathrm{LHR}}$, of the ambient plasma. These counterrotating structures were observed within the context of a lower hybrid solitary structure (LHSS), and were found to rotate in a right-handed (left-handed) sense around the geomagnetic field at frequencies above (below) $f_{\mathrm{LHR}}$, in accord with previous predictions for and observations of electric field eigenmodes within a density depletion. The presence of a narrow band feature below $f_{\mathrm{LHR}}$ indicates the presence of trapped waves, and represents clear evidence of a bound state of lower hybrid waves in the auroral ionosphere.