Modeling E-Region Artificial Periodic Inhomogeneity

Artificial periodic inhomogeneity or API experiments were conducted at the HAARP facility in Gakona, Alaska, in October 2022. The experiments concentrated on measuring ionospheric irregularities induced in the E-region. The irregularities exhibited characteristics regarding their occurrence altitudes, rise and fall times, and Doppler shifts comparable to results from experiments conducted previously at HAARP and elsewhere. The irregularities also occurred in discrete altitude bands. Seeking to quantify these results, we constructed a simple, one-dimensional fluid model which includes the effects of HF wave heating (direct and indirect) together with electron and ion cooling and thermal conduction, ion production, loss, and diffusion. Critically, the model includes a potential solver and can represent the ambipolar electric field. The model produced API irregularities in three distinct altitude bands which decayed according to the ambipolar diffusion rate.