@proceedings {931,
	title = {Analysis by Citizen Scientists of Doppler Radio Observations of the April, 2024 Solar Eclipse},
	year = {2025},
	month = {03/2025},
	publisher = {HamSCI},
	address = {Newark, NJ},
	abstract = {<p>The HamSCI community (Ham Radio Science Citizen Investigation) has analyzed high frequency radio observations of the total solar eclipse of April 8, 2024 and found interesting correlations. Nearly fifty ham radio operators recorded over 200 Doppler time series of the national time standard transmitters WWV in Colorado and CHU in Canada using specialized GRAPE (Great Radio Amateur Propagation Experiment) receivers. These observations are archived at the Personal Space Weather Station website, and cover ten frequencies from 0.6 to 25 MHz. There were over sixty different paths from transmitter to receiver at various angles across and along the path of totality from Texas to Maine. For each observation six citizen scientists collected demographic data, found distances and midpoints (where radio signals are reflected from the ionosphere), noted local eclipse information, measured the maximum Doppler shifts, counted multi-path signals, and judged the symmetry of the S-shaped Doppler curves over ingress and egress time periods. We found that the Doppler shifts depend mostly on the Sun{\textquoteright}s obscuration at the midpoint, but also on the carrier frequency and the distance between the transmitter and the receiver. At closer distances a radio wave measured a greater change in the path length as the bottom of the ionosphere retreated skyward and then returned as the Moon uncovered the Sun. \&nbsp;</p>
},
	author = {Mary Lou West and Nathaniel Frissell and Gary Mikitin and Gregory Popelas and Ronald Wilcox and McKenzie Denton and Robert Spalletta and William Engelke and Gwyn Griffiths and Steve Cerwin}
}
@proceedings {826,
	title = {Analysis of changes to propagation and refraction height on specific paths induced by the 14 October 2023 eclipse},
	year = {2024},
	month = {03/2024},
	publisher = {HamSCI},
	address = {Cleveland, OH},
	abstract = {<p>Signal and noise levels, alongside precise frequency and frequency spread measurements were collected by over 20 WsprDaemon stations prior to, during, and after the October 2023 eclipse using FST4W digital mode. By combining fortuitous home locations with eclipse-specific portable operations, augmented with multiband transmitters at selected sites, the group has gathered a rich data set over 3.5 MHz to 28 MHz. Path geometry includes along- and across-eclipse, from 10s km to over 5000 km. Different geometries, path lengths and frequencies have enabled quantitative analysis of eclipse-induced propagation changes. Reduced D region absorption resulted in 7-9 dB increase in propagated-in noise on 7 MHz at KPH/KFS. The triangular form of the noise anomaly contrasted with a flat-topped +13-15 dB signal level anomaly on 3.57 MHz on a 466 km path. Reduced F2 layer critical frequency (foF2) resulted in several phenomena on 14 MHz identified via frequency spread changes. Two-hop propagation reverted to one-hop on an 1808 km path. On a 1055 km path one-hop changed to an above-the-basic MUF mode - two-hop sidescatter - with signal levels 30 dB lower. Reduced foF2 affected two-hop along-eclipse paths of 4400 km to 5000 km from Costa Rica to Nevada and California on 28 MHz. At ca. 4400 km signals were lost twice, as the second hop, then the first, were affected, with recovery between. Signals at 5000 km were not completely lost. Simple ray-trace modelling to match the observations suggested effective sunspot number (SSNe) had dropped from 125 to ~70. As stations were GPS-disciplined or GPS-aided precise Doppler shift measurements at two-minute intervals with 0.1 Hz resolution were obtained. On a 545 km path Doppler shift at 3.57 MHz, 7 MHz and 10.14 MHz were converted to path velocities and, integrated back and forward in time from a single F2 layer height from the Pt. Arguello ionosonde, gave a credible diurnal profile of refraction height. Compared to 15th October the 14th showed a triangular-shaped height anomaly with a maximum of +33 km. These and other results illustrate the effectiveness of path-specific analysis of FST4W data for eclipse studies.</p>
},
	author = {Gwyn Griffiths}
}
