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Abstract Observations of backscatter from field‐aligned plasma density irregularities in sporadicE(Es) layers made with a 30‐MHz coherent scatter radar imager in Ithaca, New York are presented and analyzed. The volume probed by the radar lies at approximately 54° geomagnetic latitude, under the midlatitude trough and at the extreme northern edge of the zone whereEslayers are prevalent. Nonetheless, the irregularities exhibit many of the characteristics of quasiperiodic echoes observed commonly at lower middle latitudes. These include a tendency to occur in elongated bands stretching from the northwest to southeast in the Northern hemisphere separated by tens of kilometers and propagating to the southwest. In addition, the irregularities were found to exhibit finer‐scale structures with secondary bands oriented nearly normally to the primary bands. We investigate the proposition that the primary bands are telltale ofEs‐layer structuring caused by neutral Kelvin Helmholtz (KH) instability in the lower thermosphere and that the secondary bands signify secondary KH instability. Results from a 3D numerical simulation of KH support this proposition.
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Modeling E ‐Region Artificial Periodic Inhomogeneity
Abstract 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 theE‐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.
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- PAR ID:
- 10425848
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Radio Science
- Volume:
- 58
- Issue:
- 6
- ISSN:
- 0048-6604
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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