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Browsing by Author "Moses, M. L."

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    Modeling Amateur Radio Soundings of the Ionospheric Response to the 2017 Great American Eclipse
    Frissell, N. A.; Katz, J. D.; Gunning, S. W.; Vega, J. S.; Gerrard, Andrew J.; Earle, Gregory D.; Moses, M. L.; West, M. L.; Huba, J. D.; Erickson, P. J.; Miller, E. S.; Gerzoff, R. B.; Liles, W.; Silver, H. W. (2018-05-28)
    On 21 August 2017, a total solar eclipse traversed the continental United States and caused large-scale changes in ionospheric densities. These were detected as changes in medium-and high-frequency radio propagation by the Solar Eclipse QSO Party citizen science experiment organized by the Ham Radio Science Citizen Investigation (hamsci.org). This is the first eclipse-ionospheric study to make use of measurements from a citizen-operated, global-scale HF propagation network and develop tools for comparison to a physics-based model ionosphere. Eclipse effects were observed +/- 0.3 hr on 1.8 MHz, +/- 0.75 hr on 3.5 and 7 MHz, and +/- 1 hr on 14 MHz and are consistent with eclipse-induced ionospheric densities. Observations were simulated using the PHaRLAP raytracing toolkit in conjunction with the eclipsed SAMI3 ionospheric model. Model results suggest 1.8, 3.5, and 7 MHz refracted at h >= 125 km altitude with elevation angles theta >= 22 degrees, while 14 MHz signals refracted at h < 125 km with elevation angles theta < 10 degrees.
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    Observations and Modeling Studies of Solar Eclipse Effects on Oblique High Frequency Radio Propagation
    Moses, M. L.; Kordella, L. J.; Earle, Gregory D.; Drob, Douglas P.; Huba, J. D.; Ruohoniemi, John M.; Shepherd, Simon G.; Sivakumar, V (2021-03)
    The total solar eclipse over the continental United States on 21 August 2017 offered a unique opportunity to study the dependence of the ionospheric density and morphology on incident solar radiation at different local times. The Super Dual Auroral Radar Network (SuperDARN) radars in Christmas Valley, Oregon, and Fort Hays, Kansas, are located slightly southward of the line of totality; they both made measurements of the eclipsed ionosphere. The received power of backscattered signal decreases during the eclipse, and the slant ranges from the westward looking radar beams initially increase and then decrease after totality. The time scales over which these changes occur at each site differ significantly from one another. For Christmas Valley the propagation changes are fairly symmetric in time, with the largest slant ranges and smallest power return occurring coincident with the closest approach of totality to the radar. The Fort Hays signature is less symmetric. In order to investigate the underlying processes governing the ionospheric eclipse response, we use a ray-tracing code to simulate SuperDARN data in conjunction with different eclipsed ionosphere models. In particular, we quantify the effect of the neutral wind velocity on the simulated data by testing the effect of adding/removing various neutral wind vector components. The results indicate that variations in meridional winds have a greater impact on the modeled ionospheric eclipse response than do variations in zonal winds. The geomagnetic field geometry and the line-of-sight angle from each site to the Sun appear to be important factors that influence the ionospheric eclipse response.