Two Dimensional Full‐Wave Modeling of Propagation of Low‐Altitude Hiss in the Ionosphere

We investigate the propagation characteristics of low‐altitude hiss in the ionosphere by numerical simulation with a two‐dimensional full‐wave model. The simulation results demonstrate that linear mode conversion from whistler to H+ band electromagnetic ion cyclotron wave and polarization reversal occur simultaneously where wave frequency matches the H+−He+ crossover frequency. This mode conversion efficiency shows sensitive dependence on wave normal angle and plays a significant role in the propagation of whistler emission near the local proton gyro‐frequency in the ionosphere by redistributing the wave energy below and above the H+−He+ cutoff frequency, which can explain the low‐altitude hiss observed by the Freja and Detection of Electromagnetic Emissions Transmitted from Earthquake Regions satellites, respectively. The energy of whistler‐mode low‐altitude hiss emission can be transferred to reflected left‐hand polarized electromagnetic ion cyclotron through mode conversion and the efficiency reaches a maximum for intermediate incident wave normal angle (of 45°). Key Points Mode conversion from whistler to H+ band EMIC and polarization reversal occur simultaneously where wave frequency matches H+−He+ crossover frequency The wave normal angle dependence of mode conversion efficiency determines the features of low‐altitude hiss observed by low orbit satellite in the ionosphere Low‐altitude hiss emission of whistler mode can be converted to left‐hand polarized EMIC with efficiency maximized with wave normal angle near 45°