Dynamic properties of ionospheric plasma turbulence driven by high-power high-frequency radiowaves, Grach S.M., Sergeev E.N., Mishin E.V., Shindin A.V.

We report on artificial descending plasma layers created in the ionosphere $F$ region by high-power high-frequency (HF) radio waves from High-frequency Active Auroral Research Program at frequencies $f_0$ near the fourth electron gyroharmonic $4f_{\mathrm{ce}}$. The data come from concurrent measurements of the secondary escaping radiation from the HF-pumped ionosphere, also known as stimulated electromagnetic emission, reflected probing signals at $f_0$, and plasma line radar echoes. The artificial layers appeared only for injections along the magnetic field and $f_0>4f_{\mathrm{ce}}$ at the nominal HF interaction altitude in the background ionosphere. Their average downward speed $\sim 0.5\mathrm{km}/\mathrm{s}$ holds until the terminal altitude where the local fourth gyroharmonic matches $f_0$. The total descent increases with the nominal offset $f_0-4f_{\mathrm{ce}}$.

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